reserve fi,psi for Ordinal-Sequence,
  A,A1,B,C,D for Ordinal,
  X,Y for set,
  x,y for object;

theorem Th36:
  B <> {} implies A c= A*^B & A c= B*^A
proof
  assume B <> {};
  then {} in B by Th8;
  then
A1: 1 c= B by Lm1,ORDINAL1:21;
  then
A2: A*^1 c= A*^B by ORDINAL2:42;
  1*^A c= B*^A by A1,ORDINAL2:41;
  hence thesis by A2,ORDINAL2:39;
end;
