Loving, Matthew. (2011) Bullets and Balloons: French airmail during the Siege of Paris. Franconian Press (Kindle edition). https://www.amazon.com/Bullets-Balloons-French-airmail-ebook/dp/B006R656K0/ref=sr_1_1?ie=UTF8&qid=1325468042&sr=8-1
The William Fekete Collection, Sale 1082, Siegel Auction Galleries, October 21–22, 2015, "New York, New York" p. 115.
Bennett, Russell and Watson, James; Philatelic Terms Illustrated, Stanley Gibbons Publications, London (1978).
Hearst Magazines (February 1956). "Balloon Wheel Dumps Leaflets". Popular Mechanics. Hearst Magazines. p. 151. https://books.google.com/books?id=u-EDAAAAMBAJ&pg=PA151
Sudworth, John (10 November 2008). "Storm looms over N Korea balloons". BBC News. Retrieved 11 November 2008. http://news.bbc.co.uk/2/hi/asia-pacific/7719755.stm