TITLE: What is the standard reference on "infinitesimal space" in algebraic geometry??
QUESTION [7 upvotes]: infinitesimal 'spaces' is a serious issue in noncommutative (and commutative) geometry: they serve as a base of a Grothendieck-Berthelot crystalline theory and are of big importance
for the D-module theory.
Can anybody point out the standard reference for this topic? I tried to look for it at nLab, but it seems it did not tell the reference in the language of algebraic geometry. 
I am not very familiar with French,so the English manuscript is better, however, French one is fine.

REPLY [5 votes]: I think that the best reference for the infinitesimal site, especially if one is motivated to learn crystalline cohomology, is found in Grothendieck's lectures "Crystals and the De Rham Cohomology of Schemes", notes by Coates and Jussila.  This appears, in English, as number 9 of 10 in the famous "Dix Exposes".  It is an absolutely beautiful, and very readable article.  The entire Dix Exposes can be obtained freely online, as a PDF file, from Leila Schnepps's Grothendieck Circle website.