LaTeX underwent a thorough overhaul, culminating in 1994 in a new version, LaTeX2e, that unifies formerly disparate extensions, implements an optimized and efficient set of basic commands complemented by various ``packages'' to add specific functionality as needed, and incorporates a revised font selection scheme. Work continues toward the goal of LaTeX3, for which a new and improved user interface for document designers is promised.
All current AMS documentclasses and author packages require LaTeX2e, in a version no older than December 1994. Since numerous bugs have been repaired since then, a more recent version, from 1996 or later, is strongly recommended.
LaTeX can be obtained by anonymous ftp from participating sites of the Comprehensive TeX Archive Network.