Consider the following premises. t -> p_1. p_1 -> t. t <-> r. ~r. Can we infer p_1 from them?
 From t <-> r, ~r we can infer ~t. From p_1 -> t, t -> p_1 we can infer p_1 <-> t. Finally, from p_1 <-> t, ~t we can infer ~p_1, which contradicts p_1. Therefore, the answer is no.