1988*Understanding Z*.1989*The Z Notation*.1992*The Z Notation: 2nd edn*.

- The algebra of searching. 2000. (In
*Millennial Perspectives in Computer Science*) - Combinators for logic programming. 2003. (In
*The Fun of Programming*)

Mike Spivey's D.Phil thesis: *not* an introductory level text.

The essential reference for any reader or writer of Z specifications, now available on-line.