2 problems

Let $T$ be a tree extension of $S$, and let $M$ be a $T$-module such that $M_\alpha$ is an isomorphism for all arrows $\alpha$ in $T-S$. Let $M_S$ be the restriction of $M$ to $S$,…

Let $Q$ be a forest and let $M$ be a $Q$-module with ordered basis ${\mathcal B}$ such that, for every arrow $\alpha$ of $Q$, the matrix $M_\alpha$ is a block matrix … where $I$ is…