2 links
eForth and Zen
ultratechnology.com
By Dr. C.H. Ting; Offete Enterprises, 1993. Table of contents, and chapter one; compares Forth and Zen while giving overview of Forth from start to end. [Offete Enterprises]
Stack Computers: the new wave
ece.cmu.edu
By Philip J. Koopman, Jr.; Ellis Horwood, 1989. No longer printed, available on-line in HTML or PDF formats.