• The Foundations of Esterel [ PostScript ] [ PDF ]
  Gérard Berry.
  To appear in Proof, Language and Interaction: Essays in Honour of Robin Milner, G. Plotkin, C. Stirling and M. Tofte, editors, MIT Press, 2000.
• The Esterel Language Primer, version v5_91 [ PostScript ] [ PDF ]
  Gérard Berry.
  This document presents Esterel in a precise but informal way that should make most users happy in their use of the language and system. However, this is not a full-fledged reference manual. (Note: this document is also delivered with the Esterel system.)
• The Constructive Semantics of Pure Esterel [ Compressed PostScript ] [ PostScript ]
  Gérard Berry.
  This draft book presents the constructive semantics of Esterel and is the reference for the semantics. It also presents the translation of Esterel programs into circuits used in the Esterel v5 compiler. Current version : draft 3, July 2, 1999. Please discard former versions.

A general book about synchronous languages:

• Synchronous Programming of Reactive Systems.
  N. Halbwachs. Kluwer, 1993.