\item \self Given two propositional logic formulas $\varphi$ and $\psi$.
Tick all statements that are true. 
\begin{enumerate}
	\item[$\square$] If $\lnot \phi$ is not satisfiable, $\phi$ is not valid.
	\item[$\square$] If $\top \models \phi$, $\phi$ is valid.
	\item[$\square$] If $\phi \leftrightarrow \psi$ is valid, $\phi$ entails $\psi$.
	\item[$\square$] If $\phi \imp \psi$ is valid, both formulas are equivalent.
\end{enumerate}