reserve S, R for 1-sorted,
  X for Subset of R,
  T for TopStruct,
  x for set;
reserve H for non empty multMagma,
  P, Q, P1, Q1 for Subset of H,
  h for Element of H;

theorem
  P c= Q implies h * P c= h * Q
proof
  assume
A1: P c= Q;
  let x be object;
  assume x in h * P;
  then ex g being Element of H st x = h * g & g in P by GROUP_2:27;
  hence thesis by A1,GROUP_2:27;
end;
