
theorem Th27:
  for L being non empty RelStr, x being object holds x is Element of
  Subalgebras L iff x is strict directed-sups-inheriting closure System of L
proof
  let L be non empty RelStr, x be object;
  x is Element of ClosureSystems L iff x is strict closure System of L by Th16;
  hence thesis by Def7,YELLOW_0:58;
end;
