Vandeghen, A. (1964), «Mathematical Notes: Soddy's Circles and the De Longchamps Point of a Triangle», The American Mathematical Monthly, 71 (2): 176–179, JSTOR2311750, MR1532529, doi:10.2307/2311750.
books.google.com
Lazzeri, G. (1907), «Gastone Gohierre de Longchamps», Periodico di Matematica per l'Iinsegnamento Secondario, Ser. III (em italiano), 4: 53–59.
Vandeghen, A. (1964), «Mathematical Notes: Soddy's Circles and the De Longchamps Point of a Triangle», The American Mathematical Monthly, 71 (2): 176–179, JSTOR2311750, MR1532529, doi:10.2307/2311750.
jstor.org
Vandeghen, A. (1964), «Mathematical Notes: Soddy's Circles and the De Longchamps Point of a Triangle», The American Mathematical Monthly, 71 (2): 176–179, JSTOR2311750, MR1532529, doi:10.2307/2311750.