 reserve X,a,b,c,x,y,z,t for set;
 reserve R for Relation;

theorem :: Proposition 18
  for R1, R2 being non empty RelStr st
    the carrier of R1 = the carrier of R2 &
    LAp R1 cc= LAp R2 holds
      the InternalRel of R2 c= the InternalRel of R1 by Prop18;
