C
C     ..................................................................
C
C        USER-SUPPLIED SPECIAL SUBROUTINE - BOOL
C
C        THIS SPECIAL SUBROUTINE ILLUSTRATES AN EXTERNAL SUBROUTINE
C        CALLED BY SUBROUTINE SUBST.
C
C        IF DIFFERENT PROPOSITIONS ARE USED FOR DIFFERENT PROBLEMS IN
C        THE SAME RUN, DIFFERENT SUBROUTINES WITH APPROPRIATE PROPOSI-
C        TIONS MUST BE COMPILED UNDER DIFFERENT NAMES.  IF SO, THESE
C        SUBROUTINE NAMES MUST BE DEFINED BY AN EXTERNAL STATEMENT
C        APPEARING IN THE MAIN PROGRAM WHICH CALLS SUBST.  THEN, FOR
C        EACH PROBLEM, SUBST IS CALLED WITH A PROPER SUBROUTINE NAME
C        IN ITS ARGUMENT LIST.
C
C     ..................................................................
C
      SUBROUTINE BOOL(R,T)
      DIMENSION R(1)
C
      T=R(1)*R(2)
C
      RETURN
      END