i need a reference of the following proof, i hope someone can show me a book where i can find it.
Theorem:
Let $U$ be a cover of a top space $X$ and $F_i$ a sheaf on $U_i$. If there exists a morphism of sheaves like $\theta_{ij}: F_i\mid_{U_{ij}} \longrightarrow F_j\mid_{U_{ij}}$, then there exists a sheaf $F$ on $X$ such that $\theta_i : F\mid_{U_{ij}} \longrightarrow F_i$ is an isomorphism.
i could not find a proof for that on my own, hopefully someone can help me