The Free On-line Dictionary of Computing (19 January 2023):

Bertrand

   (Named after the British mathematician Bertrand Russell
   (1872-1970)).  Wm. Leler.  Rule-based specification language
   based on augmented term rewriting.  Used to implement
   constraint languages.  The user must explicitly specify the
   tree-search and the constraint propagation.

   (ftp://nexus.yorku.ca/pub/scheme/scm/bevan.shar).

   ["Constraint Programming Languages - Their Specification and
   Generation", W. Leler, A-W 1988, ISBN 0-201-06243-7].