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Charles E. Apgar

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Charles E. Apgar
BornJune 28, 1865 (1865-06-28)
Gladstone, New Jersey[1]
DiedAugust 17, 1950 (1950-08-18) (aged 85)
Westfield, New Jersey[2]
SpouseHelen May Clarke
Children3
Call sign2MM
Signature
Chas. E. Apgar

Charles Emory Apgar (June 28, 1865 – August 17, 1950) was an American business executive and amateur radio operator. He is known for making early recordings of radio transmissions at the start of World War I.[3] The recordings that he made of a wireless telegraphy station owned by a German Empire based company operating from the United States were used to expose an espionage ring.[2] They provided evidence of clandestine messages being sent in violation of a prohibition intended to maintain United States neutrality.[4] This proof of illicit operation led to the government seizing control of the facility to stop the activity.[1] Apgar's efforts received extensive coverage in newspapaers and technical science magazines at the time.[5][6][7] His contributions were praised by government investigators.[8][9] Publications continued to remark on his work many years later.[10][11][12][13]

Biography

Apgar was born in Gladstone, New Jersey. He was a student at Centenary Collegiate Institute in 1880.[a][14] Apgar attended Wesleyen University in 1887-88 though he never graduated.[15] He married Helen May Clarke and they had three children: Charles Emory Apgar Jr. who died at a young age, Lawrence C. Apgar who became a professor of music, and Dr. Virginia Apgar who was a pioneer in obstetrics and neonatology.[16][17]

Apgar was a member of the Methodist Episcopal Church in Westfield, New Jersey.[16] He became a Master Mason at a Freemasonry lodge in 1906.[18] He worked as a business execuctive in a variety of positions for New York Life Insurance Company and later for the brokerage firm Spencer Trask & Co.[1] In 1915, during the time when his recordings gained notoriety, he was employed as a salesman for Haynes Automobile Company.[5] He was also an amateur astronomer whose calculations of the motions of Jupiter's satelites were regularly published in the Journal of the Royal Astronomical Society of Canada.[3] He died in Westfield at the age of 85.

Amateur radio

The station at his home including equipment that he built.

Apgar became interested in wireless telegraphy after reading about an amateur who had heard election returns transmitted by a newspaper on election night (i.e. before the results could be widely distributed the following morning.) He built his first "home-made" wireless telegraphy equipment on December 11, 1910. He listened to news bulletins from the New York Herald station OHN in Manhattan.[19] The station had been created to send news to approaching ocean liners and receive reports about their voyage.[20]

After the passage of the Radio Act of 1912 he was licensed to use the call sign 2MM from 1913 to 1915. At the experimental wireless station inside his home in Westfield he operated a 450 Watt amateur station.[21] The equipment that he constructed could use a wavelength of 8,000 metres (37 kHz) during an era when few amateurs went beyond 600 metres (500 kHz). It was described as a "high-grade plant" of "extraordinary efficiency."[22] In April 1913 he became an associate member of the recently founded Institute of Radio Engineers.[23] He was an early participant in the American Radio Relay League (ARRL) by October 1913.[24]

Circuit diagram of his station connected to a phonograph recorder.

He built equipment that could greatly amplify the sound from his radio receiver. Connected to a device he built that he called a "loud talker-horn" (an early type of loudspeaker) it could be heard 600 feet (180 m) away. An editor of a magazine was so impressed that he enthusiastically described it as "One of the greatest feats ever produced by any amateur..."[19] Apgar also devised a method to record the signals from stations that he listened to. (see Wireless recordings) His accounts of the equipment that he used to make the recordings were featured in magazines such as The Wireless Age and Electrical Experimenter.[25][19] His recordings were colloquially referred to as "canned messages."[5]

Wireless recordings

Apgar's equipment was mostly homemade with the exception of an improved Audion designed by Edwin Howard Armstrong (that was part of the circuit used to detect and amplify the signal) and the headphones.[25] It was connected to a Dictaphone which allowed him to record Morse code transmissions on wax cylinders made by Edison Manufacturing Company.[7] His first recording was made October 12, 1913 of the New York Herald station which by this time was using the callsign WHB.[b] By October 1914 he had recorded other transmissions including the United States Navy station NAA sending time signals.[19]

Sayville station

Painting on the cover of the Aug. 1915 issue of The Electrical Experimenter titled "Sayville (N. Y.) Wireless Receiving German War Report."

Apgar then became interested in wireless station WSL in Sayville, New York on the coast of Long Island.[19] It was a high power commercial station designed for long distance communication.[26] The station was operated by the Atlantic Communications Company which was primarily owned by the German company Telefunken. The station was built to establish two-way communication with the Nauen Transmitter Station POZ in Europe which was jointly owned by the Imperial German Army and Imperial Mail.[4] Nauen was the only station in Europe capable of transmitting to North America at the time. It was mostly sending news that Sayville received and distributed by telegraph to American wire services.[27]

During construction in August 1912 the Navy began observing Sayville because it was reportedly controlled by a company that was under the influence of the German government. The company claimed that it had no such connection.[28] It had just became operational in July 1913. These were the first regular transmissions between the United States and Germany.[29] The equipment that Apgar built was sensitive enough that he also often clearly heard the Nauen station that was 4,000 miles (6,400 km) distant.[6] Apgar listened to Sayville and made his first recordings of it in November 1913.[8] In February 1914 Apgar sent some of these cylinder recordings to the operators of Sayville, at their request.[6]

At the start of World War I the United States declared that it was neutral in the conflict. In August 1914 President Woodrow Wilson issued an executive order that prohibited radio communication of an "unneutral nature" from United States territory. Any communication that could aid military activities would have jeopardized neutrality. This was due to an article in the Hague Convention that stated: "belligerents are forbidden to erect on the territory of a neutral power a wireless telegraphy station or other apparatus for the purpose of communicating with belligerent forces on land or sea." The Navy stationed personel at the facility to inspect the messages before they were sent and enforce the order if needed. Sayville was considered one of the three most important stations to which this order applied.[30]

During the war the German transatlantic telegraph cable was intentionally cut by the British which resulted in the German embassy becoming heavily reliant on the new wireless station.[31][32] The summer residence of German ambassador Johann Heinrich von Bernstorff in Cedarhurst, New York, on Long Island had a direct telegraph line to Sayville to relay diplomatic communication to Germany by wireless.[5] The Navy began to have doubts about the legitimate operation of the station after they learned that a technical advisor there, physicist and engineer Jonathan Zenneck, was a captain in the German marines.[4] The station was soon suspected of violating the presidential prohibition by including secret messages despite the government censorship.[33]

During the summer months reception of wireless signals was difficult due to adverse atmospheric conditions which increased static. Long distance communication was only possible during the night for brief intervals. To alleviate this limitation Sayville "quietly" (such that only a few government officials were aware of it) made major improvements to the equipment. In April 1915 the transmitter was upgraded from 35 to 100 kilowatts and three 492 feet (150 m) tall antenna towers were installed transforming it into one of the most powerful transatlantic stations in this part of the world.[31] By May the Telefunken station at Sayville and another at Tuckerton, New Jersey, were accused of sending messages to a German U-boat providing information that allowed the submarine to "ambush" and sink the RMS Lusitania. This led to greater scrutiny of activity at the station.[34]

Investigation

Apgar producing "canned" wireless messages on his recorder, 1915.

Apgar noticed the peculiar messages sent from Sayville.[35] He informed an inspector from the government Radio Bureau about the odd messages and his recordings of them.[10] Apgar knew L. R. Krumm, Chief Radio Inspector for the Port of New York and New Jersey, and the inspector had been aware of his recordings for some time.[8] Krumm visited Apgar to examine his apparatus and witness a demonstration.[25] Krumm then alerted the United States Secret Service and suggested that they contact Apgar.[36] At the request of William J. Flynn, Chief of the Secret Service, Apgar commenced making regular recordings of the station on June 7, 1915. This continued every night for two weeks.[6] He alternated between two cylinder recorders to ensure uninterrupted capturing of the messages while he replaced a full cylinder with a new blank one.[25] During this time he made 11 hours of permanent recordings that captured 25,000 words transmitted by the station. Apgar was paid for this work by the government through Flynn.[8]

The "perforator apparatus" used at Sayville to punch Morse code on paper tape.

The original messages, approved by government censors, were suspected to contain subsequently altered Morse code that could be used as a cipher. The Sayville station was equipped with a type of Wheatstone system that used perforated paper tape to automatically key the transmitter.[8] An operator produced the tape containing the message before sending. The tape was then run through the transmitter control equipment at a high speed.[26] It operated at 150 wpm (words per minute), significantly faster than the 50 wpm that a highly skilled operator could send manually.[37] The transmissions were so rapid that it made the messages unintelligible to a listener. It was a "meaningless, musical hum or buzz which puzzled all hearers" and sounded like a "titanic bumblebee."[36] Apgar transcribed the previous night's recording each morning by playing the wax cylinder on a phonograph at a much slower speed. He would then telephone the Secret Service to file a report about the transmissions. He made 175 recordings of these suspicious messages, each cylinder containing 4 minutes of transmission time. In addition to his daily reports he turned over the original cylinder recordings to the government.[8]

The messsages from Sayville were then discussed by the Cabinet of the United States.[38] The recordings proved that the suspected covert messages were present within the approved transmissions.[37] Apgar's "canned" messages are credited with establishing the truth about the Sayville station's activity, though the exact nature of the messages on the recordings remained an official secret.[5] This evidence led to Wilson ordering the Navy to seize the facility on July 8, 1915. The Navy operated the station in trust to send commercial messages for the duration of the war[4]

Encoded messages

"The above 'code' diagram shows how secret cipher messages could be interspersed through regular messages."[37] In example "No 2" the Morse code for the letter "B" has been changed to "6E" by adding two extra dots. (see text)

After listening to the recordings it took the Secret Service four months to decode the hidden messages. A covert message interspersed with the censor approved text might include the addition of "5-8-K-14-B" for example. This would direct the recipient to the fifth and eighth words on page 11, and the fourteenth word on page 2, of a rare edition of a German dictionary.[39] (see example "No 2" in figure)

A variety of alternate methods of encoding were used. For long distance communication in this era it was standard practice to employ repetition to ensure successful reception. The message "Pr 3." would be sent "Pr 3. Pr 3." for example. The Sayville transmissions varied this practice by sometimes sending "Pr Pr 3 Pr. 3." – a significat variation that a casual listener might overlook. These were alleged to be a key to an acrostic code.[5]

Other methods of obfuscation included using innocuous English or American sounding fictitious names such as "Frederick Chappel" to refer to the German submarine Deutschland or "Theodore Hooper" as a code name to refer to Capt. von Papen, the German military attaché in Washington, DC. The phrase "Expect father to-morrow" would be interpreted as "The political situation between America and Germany grows worse. It is imperative that you take care of your New York affairs."[40] These names and phrases were concealed in communications that masqueraded as commercial messages. Copies of these were provided to the government by the Providence Journal which accused the German Embassy of revealing secret information about the movements of the allied navy fleet. The headline of the story was subtitled: "Ambassador Breaks Pledges and with Captain Boy-Ed Has Tricked United States Authorities for Months."[41]

Significance and legacy

Cover story about Apgar in The Wireless Age, Sept. 1915.

Hiram Percy Maxim has noted that he and other amateurs also noticed these messages: "Apgar, the old sleuth, smelled something just about the time the rest of us did."[35] Flynn describes the importance of Apgar's contributions to the government seizure: "It was really his absolutely faithful records of all of the signals sent out from Sayville that caused the United States to seize the famous station."[35] Extensive coverage in the media in 1915 included a magazine cover story about Apgar that referred to him as "A Wireless Detective in Real Life."[8] (see illustration)

A photo of Apgar published in Popular Radio, Nov. 1923.

A 1923 article by William J. Burns, then director of the Bureau of Investigation,[c] in Popular Radio included a photo of Apgar. It was captioned "The Radio Detective Who Unfathomed the Famous 'Nauen Buzz'" and the description read:[9] (see photo)

"During the early days of the World War the incredibly rapid and undecipherable radio signals between the most powerful broadcasting station in Germany and the station of the "Telefunken Company" at Sayville, Long Island, N. Y., aroused the attention of the U. S. officials. But it was radio amateur, Charles E. Apgar of Westfield, N. J., who finally found the solution by means of amplifiers that recorded these signals on wax phonograph cylinders. By this means the messages were de-coded – and the Long Island station was promptly seized. This picture shows Mr. Apgar operating the same apparatus which he used on that historic occasion."

The Sayville incident has been described as one of the first "overt acts" that led to American entry into World War I two years later. The specific information recorded on the wax cylinders remained a closely guarded secret in the government archives for many years.[12]

The cylinders that he recorded were acquired by NBC in 1934. An example was displayed, along with the original receiving set that Apgar donated, as part of a museum exhibit in the lobby of Rockefeller Center.[12] Apgar's work received renewed attention early during World War II when amateur radio operators began listening for "fifth column" activity such as odd coded messages sent from "mystery" stations.[13] His work was noted by the ARRL in 2015 during a commemoration held on the 100th anniversary of the sinking of Lusitania.[42] At this time he was also inducted into the CQ Amateur Radio Hall of Fame.[43]

Some of Apgar's homemade equipment has been preserved at The Henry Ford museum.[44] His original wax cylinders are believed to be lost, but some samples of his recordings survive.[45] An interview of Apgar by George Hicks was broadcast on station WJZ and the NBC Blue Network on Dec. 27, 1934. A tape copy of the original aluminum phonograph discs and a transcript is in the Recorded Sound Collection of the Library of Congress.[46] A recording of this broadcast donated by Thorn Mayes is in the collection of the Antique Wireless Association.[47] Broadcast historian Elizabeth McLeod considers Apgar's cylinders to be the earliest surviving recordings of a radio transmission based on research done by Dr. Michael Biel.[45][48]

Fictional portrayal

After Flynn's retirement from the Secret Service his experiences were adapted by Courtney Ryley Cooper into a 20-part spy thriller. These were published as weekly installments in The Atlanta Constitution's magazine section during 1918. The title of the series was The Eagle's Eye: A True Story of the Imperial German Government's Spies and Intrigues in America. An episode titled "The Great Hindu Conspiracy"[d] begins with a minor character named Charles E. Apgar. He is described as a "wireless expert" who is recruited to record messages from Sayville. The fictional Apgar is said to be "quite a linguist." The letter combinations hidden in the messages remind the character of Hindi. This observation is an important clue in the espionage investigation featured in the storyline.[49] The episodes were also released as a serial film titled The Eagle's Eye. Fifteen of the episodes were republished as chapters in a book the following year, though the story with Apgar was not included.[50]

Notelist

  1. ^ Before 1910 it was a coeducational preparatory school.
  2. ^ A different station in Kansas City, Missouri, was licensed to broadcast as WHB starting in the early 1920s.
  3. ^ The BOI was the predecessor to the Federal Bureau of Investigation.
  4. ^ This is a reference to an actual Hindu–German Conspiracy and the subsequent trial.

References

  1. ^ a b c "Charles E. Apgar, Radio Expert, 86; Jersey 'Ham' Operator Dies – Recorded Code Messages From Sayville Station in 1915". New York Times. August 19, 1950. p. 12. Charles E. Apgar, a 'ham' radio operator who recorded code messages during World War I from a German station at Sayville, L.I., which proved to be tips to German submarines on the movements of neutral ships and caused the Government to seize the station...
  2. ^ a b "Charles E. Apgar, Helped Trap Spies: Intercepted Radio Signals Guiding U-Boats in 1915". New York Herald Tribune. August 19, 1950. p. 8. Charles E. Apgar, eighty-five, one of the central figures in a 1915 expose of a German espionage ring, died yesterday at his home, 549 Carleton Road. Mr. Apgar was engaged in electrical research at a laboratory in his home on Carleton Road in 1915 when he intercepted and made recordings of wireless signals by spies in Union County, N. J., to direct German submarine commanders off the East Coast. His findings, later decoded by the Secret Service, enabled them to locate the spy headquarters and a wireless transmitter at Sayville, L. I.
  3. ^ a b Hogg, F.S. (December 1950). "Notes and Queries – Obituary: Mr. Charles E. Apgar". Journal of the Royal Astronomical Society of Canada. 44: 247. Bibcode:1950JRASC..44..247H. Archived from the original on 2019-12-29. Retrieved 2013-02-21.
  4. ^ a b c d Winkler, Jonathan Reed (2009). "Neutrality and Vulnerability". Nexus. Harvard University Press. pp. 51–52. ISBN 9780674033900.
  5. ^ a b c d e f "Radio Secrets of Sayville in 'canned' Form: Uncle Sam Got Records of Messages on a Phonograph". Detroit Free Press. July 18, 1915.
  6. ^ a b c d Gernsback, Hugo, ed. (September 1915). "Why Sayville Radio Station Was Closed" (PDF). The Electrical Experimenter. Vol. III, no. 5. New York. pp. 210, 215. Retrieved 22 December 2019.
  7. ^ a b "The Quenching of Sayville: The close of a Sordid Story". The Wireless World. Vol. 3, no. 32. November 1915. pp. 515–517. Retrieved 29 December 2019.
  8. ^ a b c d e f g "A Wireless Detective in Real Life" (PDF). The Wireless Age. Vol. 2, no. 11. New York: Marconi Publishing. September 1915. pp. 872–877. Retrieved 26 December 2019.
  9. ^ a b Burns, William J. (November 1923). "Radio puts on Gum Shoes". Popular Radio. Vol. IV, no. 5. New York. p. 349. Retrieved 1 January 2020.
  10. ^ a b Taussig, Charles William (1922). "What the amateur has done in radio". Book of Radio. New York: Appleton and Company. pp. 194–195. ASIN B0040X4OXM.
  11. ^ "Hartford Is Capital of American Relay League". Providence Sunday Jounral. October 13, 1929.
  12. ^ a b c "War-Time Wireless Signals in Wax: New Addition to Museum of Radio Relics". Daily Boston Globe. June 3, 1934. p. A49.
  13. ^ a b "55,000 Amateur Radio 'Hams' Aid in Drive on Fifth Column". New York Herald Tribune. September 29, 1940. To date there has been nothing to compare with the World War service of Charles Apgar...
  14. ^ "Charles E. Apgar Material, 1880, 1906". Mount Holyoke and Hampshire College archives. Five College Consortium. Archived from the original on 31 December 2019. Retrieved 31 December 2019.
  15. ^ The Wesleyan University Bulletin. Vol. 10. Middletown, CT: Wesleyan University. May 1916. p. 61.
  16. ^ a b "Personals and Church News". The Christian Advocate. New York. April 28, 1904. p. 672. Retrieved 23 December 2019.
  17. ^ "Mrs. Charles E. Apgar". New York Times. March 29, 1969. p. 35.
  18. ^ Proceedings of the M. W. Grand Lodge of Free and Accepted Masons of the State of New Jersey. Trenton, NJ: MacCrellish & Quigley. 1907. p. XLI.
  19. ^ a b c d e Apgar, Charles E. (November 1915). Gernsback, Hugo (ed.). "The Amateur Radio Station Which Aided Uncle Sam" (PDF). The Electrical Experimenter. Vol. III, no. 7. New York. pp. 337–338. Archived (PDF) from the original on 23 December 2019. Retrieved 22 December 2019. Naturally the matter of making permanent records occurred to me about this time. I bought a second-hand phonograph and on Oct. 28, 1913, made my first record of wireless; this being 'press' sent out by the New York Herald station at the Battery in New York.
  20. ^ "Triumph of Wireless Telegraphy". The Nashville American. Nashville, Tennessee. September 19, 1901.
  21. ^ Radio Service, Department of Commerce (July 1, 1915). Radio Stations of the United States. Washington: Government Printing Office. p. 82.
  22. ^ Cite error: The named reference NYH1950 was invoked but never defined (see the help page).
  23. ^ Year Book: 1914. New York: The Institute of Radio Engineers. 1914. p. 24.
  24. ^ Harold P. Westman, ed. (1945). "Amateur Radio and the A.R.R.L.". Radio Pioneers, 1945. New York: Institute of Radio Engineers. pp. 28–31.
  25. ^ a b c d Apgar, Charles E. (September 1915). "Making the Records from Sayville: A Description of My Set and How I worked It" (PDF). The Wireless Age. Vol. 2, no. 11. New York: Marconi Publishing. pp. 877–880. Retrieved 26 December 2019.
  26. ^ a b Van Der Woude, Fritz; Seelig, Alfred E. (July 1913). "The High Power Telefunken Radio Station at Sayville, Long Island". Proceedings of the Institute of Radio Engineers. 1 (3): 23–35. doi:10.1109/JRPROC.1913.216587.
  27. ^ Evans, Heidi J. S. (2010). ""The Path to Freedom"? Transocean and German Wireless Telegraphy, 1914-1922" (PDF). Historical Social Research. 35 (1): 208–233. doi:10.12759/hsr.35.2010.1.209-233.
  28. ^ "4,000 Miles by Wireless: Nauen, Germany, Communicates with the Station at Sayville, L.I.". New York Times. May 10, 1913.
  29. ^ "Send a Wireless Through to Berlin". New York Times. July 15, 1913. p. 1.
  30. ^ "Check on Wireless to keep Neutrality". New York Times. August 6, 1914. p. 4.
  31. ^ a b "Germans Treble Wireless Plant". New York Times. April 23, 1915.
  32. ^ Douglas B., Craig (2003). "The Radio Age: The Growth of Radio Broadcasting, 1895-1940". Fireside Politics: Radio and Political Culture in the United States, 1920-1940. John Hopkins University Press. pp. 3–4. ISBN 9780801875120.
  33. ^ "German Wireless again: Sayville Station Still Sending Out Code Messages, it is said". New York Times. August 15, 1914. p. 4.
  34. ^ "Fear Wireless Trap Caught Lusitania: Close Scrutiny of All Messages at Two German Stations Called For". New York Times. May 10, 1915. p. 7.
  35. ^ a b c Bartlett, Richard A. (2015). "Amateurs During World War I". The World of Ham Radio, 1901-1950: A Social History. McFarland. pp. 48, 52, 263. ISBN 9781476612607.
  36. ^ a b By One of Them (July 1922). "The Secret Service of the Air". Popular Radio. Vol. I, no. 3. New York. p. 349. Retrieved 22 December 2019.
  37. ^ a b c Gernsback, Hugo, ed. (September 1915). "Sayville, the News-Way to Berlin" (PDF). The Electrical Experimenter. Vol. III, no. 5. New York. pp. 209–210. Retrieved 22 December 2019.
  38. ^ "Plant Under Suspicion: Officers Think German Station May Send Messages to Submarines". New York Times. July 1, 1915. pp. 1–2.
  39. ^ "Out of the Air". The Sun. Baltimore, MD. June 12, 1921. p. F2.
  40. ^ Jones, John Price; Hollister, Paul Merrick (1918). "The Wireless System". The German Secret Service in America. Boston: Small, Maynard & Company. pp. 43–59.
  41. ^ "Providence Journal Collects All Wireless Messages and Forwards Them to Government". Providence Daily Journal. July 1, 1915. pp. 1–2. German Embassy Uses Station Constantly to Supply Secret Information to Berlin Concerning Movement of Allied Armies and Fleets
  42. ^ "The Sinking of the Lusitania: A Ham Radio Connection". ARRL. American Radio Relay League. April 29, 2015. Archived from the original on 24 December 2019. Retrieved 29 December 2019.
  43. ^ "CQ Names 2015 Hall of Fame Inductees". ARRL. American Radio Relay League. May 15, 2015. Archived from the original on 24 December 2019. Retrieved 29 December 2019.
  44. ^ "Digital Collections". Benson Ford Research Center. The Henry Ford. Archived from the original on 16 May 2019. Retrieved 27 December 2019.
  45. ^ a b McLeod, Elizabeth. "Documenting Early Radio: A Review of Existing Pre-1932 Radio Recordings". Old Time Radio Library. Archived from the original on 2016-02-19. Retrieved 2016-01-24.
  46. ^ "Interview with Charles E. Apgar". SONIC – Sound ONline Inventory Catalog. Library of Congress. Archived from the original on 29 October 2019. Retrieved 28 December 2019. Interview with Charles E. Apgar who for fourteen nights around June 18, 1915 recorded messages broadcast by a German owned and operated radio station in Sayville, Long Island. The U.S. government asked Apgar to do this because the station was broadcasting encoded information to Germany about American shipping for German submarines off-shore. Based on Apgar's recordings, the government seized the station on July 8, 1915. Apgar used his homemade radio receiver and an Edison cylinder phonograph to record the messages. During the interview he plays two of the original cylinders.
    This audio cassette was copied from two 12-inch 78rpm aluminum discs which the Library does not own.
  47. ^ "Mayes Tape Library Index". Antique Wireless Society. Archived from the original on 30 May 2019. Retrieved 28 December 2019.
  48. ^ Biel, Michael Jay (1978). The Making and Use of Recordings in Broadcasting Before 1936 (Doctoral dissertation). Northwestern University.
  49. ^ Flynn, William J. (August 25, 1918). "The Eagle's Eye: True Story of the Imperial German Government's Spies and Intrigues in America". The Atlanta Constitution. No. 18. p. 12F.
  50. ^ Cooper, Courtney Ryley; Flynn, William James (1919). The Eagle's Eye: A True Story of the Imperial German Government's Spies and Intrigues in America from Facts Furnished by William J. Flynn, Recently Retired Chief of the U.S. Secret Service. New York: McCann. ASIN B009QJTQCO. {{cite book}}: Unknown parameter |lastauthoramp= ignored (|name-list-style= suggested) (help)
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