Gli amori degli uomini. Saggio di una etnologie dell'amore. 2 vols.

Digital facsimile of the 1886 edition from the Hathi Trust at this link.

Translated into English "from the latest Italian edition, as approved by the author, by Samuel Putnam, edited with an introduction by Victor Robinson" as Sexual relations of mankind, New York: Eugenics Publishing Company (1935).