theorem Th36:
  SF (\) A is MSSubsetFamily of M
proof
  SF c= bool M by PBOOLE:def 18;
  then
A1: SF (\) A c= (bool M) (\) A by PBOOLE:53;
  (bool M) (\) A c= bool M by PBOOLE:56;
  then SF (\) A c= bool M by A1,PBOOLE:13;
  hence thesis by PBOOLE:def 18;
end;
