reserve X,Y,Z,x,y,z for set;

theorem
  Total X is strongly_connected
proof
  let x,y be object;
  assume x in field Total X & y in field Total X;
  then x in X & y in X by ORDERS_1:12;
  then [x,y] in [:X,X:] by ZFMISC_1:87;
  hence thesis by EQREL_1:def 1;
end;
