reserve i,j,e,u for object;
reserve I for set; 
reserve x,X,Y,Z,V for ManySortedSet of I;
reserve I for non empty set,
  x,X,Y for ManySortedSet of I;

theorem
  X overlaps X implies X <> EmptyMS I
proof
  X = X (/\) X;
  hence thesis by Th127;
end;
