1. J.S.B. Haldane, Of Possible Worlds, and Other Essays (Chatto & Windus, London, 1932)
2. M. Tabarrini, G. Milanesi, (eds.), Trattato della pittura di Leonardo Da Vinci, condotto sul Codex Vaticanus Urbinate 1270. Unione Cooperativa Editrice, Roma (1890) [A modern reprint of the Urbinate 1270, assembled around the years 1520–25 by the Milanese painter Leonardo Melzi, former pupil of Leonardo]
3. J. Taylor, The structure of singularities in soap-bubble-like and soap-film-like minimal surfaces. Ann. Math. (2nd ser.) 103, 489–539 (1976)
4. J. Richard, (ed.), Résultats des campagnes scientifiques accomplies sur son yacht par Albert Ier, prince souverain de Monaco. Fasc. X and XXXV, Imprimerie de Monaco (1896-1911) [released for public domain: archive.org/details/rsultatsdescam10albe]
5. W. D’Arcy Thompson, On Growth and Form, 1st edn, 1971. Cambridge University Press, New York (1945) [released for public domain: archive.org/details/ongrowthform00thom]