The Free On-line Dictionary of Computing (30 December 2018):

Parlog

   Clark & Gregory, Imperial College 1983.  An AND-parallel
   Prolog, with guards and committed choice nondeterminism
   (don't care nondeterminism).  Shallow backtracking only.

   Implementations: MacParlog and PC-Parlog from Parallel Logic
   Programming Ltd., Box 49 Twickenham TW2 5PH, UK.

   See also SPM.

   (ftp://ftp.inria.fr/lang/Parlog.tar.Z).  E-mail:
   .

   ["Parlog: A Parallel Logic Programming Language", K.L. Clark
   and S. Gregory, Imperial College, London, May 1983].
   ("Parlog83", in which the ouput mechanism was assignment).

   ["Parallel Logic Programming in PARLOG, The Language and Its
   Implementation", S. Gregory, A-W 1987].  ("Parlog86", in which
   the output mechanism was unification, as in GHC).  (See
   Strand).