“The greatest thing in the world is to know how to belong to oneself.”

The Tragic Sense of Life (1913), Conclusion : Don Quixote in the Contemporary European Tragi-Comedy

Savoir se libérer n'est rien; l'ardu, c'est savoir être libre.
The Immoralist, Chapter 1 http://books.google.com/books?id=MPmRAAAAIAAJ&q=%22Savoir+se+lib%C3%A9rer+n'est+rien+l'ardu+c'est+savoir+%C3%AAtre+libre%22&jtp=17#v=onepage (1902)
The Immoralist (1902)

Original: (it) Chi sa donare vero amore appartiene esclusivamente a quella rarità di esseri viventi, capaci di cambiare il mondo.
Source: prevale.net

Source: Literary Years and War (1900-1918), The Riddle Of The Sands (1903), p. 1.

trans. Michael Chase (1995), p. 90
La Philosophie comme manière de vivre (2001)

Pithy Aphorisms: Wise Saying and Counsels, Edited by Mansoor Limba, Tehran: The Institute for Compilation and Publication of Imam Khomeini’s Works -- International Affairs Department, p. 4.
Theology and Mysticism

In his video account on the creation of TeX http://www.webofstories.com/people/donald.knuth/52?o=SH, he comments that Xerox offered to allow him to use their equipment, but that the fonts he created would belong to them.

Letter to Mr. Fitzpatrick (30 July 1789) on the fall of the Bastille, printed in J. Russell (ed.), Memorials and Correspondence of Charles James Fox. Volume II (London: Richard Bentley, 1853), p. 361.
1780s

As quoted in Perfecting Ourselves : Coordinating Body, Mind, and Spirit (2002) by Aaron Hoopes, p. 64
Posthumous publications