reserve i, x, I for set,
  A, B, M for ManySortedSet of I,
  f, f1 for Function;
reserve SF, SG for SubsetFamily of M;

theorem Th8: :: MSSUBFAM:39
  A c= M & B c= M implies {A,B} is SubsetFamily of M
proof
  assume A c= M & B c= M;
  then {A} is SubsetFamily of M & {B} is SubsetFamily of M by Th7;
  then {A} \/ {B} is SubsetFamily of M by Th3;
  hence thesis by ENUMSET1:1;
end;
