reserve F for Field,
  a,b,c,d,e,f,g,h for Element of F;
reserve x,y for Element of [:the carrier of F,the carrier of F,the carrier of
  F:];
reserve F for Field;
reserve PS for non empty ParStr;
reserve x for set,
  a,b,c,d,e,f,g,h,i,j,k,l for Element of [:the carrier of F,
  the carrier of F,the carrier of F:];
reserve a,b,c,d,p,q,r,s for Element of MPS(F);
reserve PS for ParSp,
  a,b,c,d,p,q,r,s for Element of PS;

theorem Th26:
  a<>b & p,q '||' a,b & a,b '||' r,s implies p,q '||' r,s
proof
  assume that
A1: a<>b and
A2: p,q '||' a,b and
A3: a,b '||' r,s;
  a,b '||' p,q by A2,Th23;
  hence thesis by A1,A3,Def11;
end;
