reserve T for non empty Abelian
  add-associative right_zeroed right_complementable RLSStruct,
  X,Y,Z,B,C,B1,B2 for Subset of T,
  x,y,p for Point of T;

theorem
  X (O) B c= (X \/ Y) (O) B
proof
  X c= X \/ Y by XBOOLE_1:7;
  hence thesis by Th45;
end;
