Brian W. Kernighan: Programming in C: A Tutorial
   This ``tutorial'' is presented as a historical document, not as a tutorial. Although it has lost little of its didactic value, it describes a language that C compilers today do no longer understand: the C of 1974, four years before Kernighan and Ritchie
   http://www.lysator.liu.se/c/bwk-tutor.html

Primeval C: two very early compilers
   Very early C compilers and language.
   http://www.cs.bell-labs.com/who/dmr/primevalC.html

The Development of the C Language
   Article by Dennis M. Ritchie. History C programming language.
   http://cm.bell-labs.com/cm/cs/who/dmr/chist.html