theorem Th43:
  not <%>E in rng dom (the Tran of TS) implies not [[x, z], [y, z]
  ] in ==>.-relation(TS)
proof
  assume not <%>E in rng dom (the Tran of TS);
  then not x, z ==>. y, z, TS by Th28;
  hence thesis by Def4;
end;
