Let p, q and r be three statements, then (p→q)→r is equivalent to
(p∧~q)∧r
(p∧~q)∨r
(p∧q)∧~r
(p∧~q)∧~r
(p→q)→r≡(~p∨q)→r≡[~(~p∨q)]∨r≡[p∧(~q)]∨r