theorem
  Z_Lin(A /\ B) c= Z_Lin(A) /\ Z_Lin(B)
proof
  Z_Lin(A /\ B) c=Z_Lin(A) & Z_Lin(A /\ B) c=Z_Lin(B) by Th13,XBOOLE_1:17;
  hence thesis by XBOOLE_1:19;
end;
