I am looking for a suitable reference to put in a bibliography for the following fact:
Let $f: X \rightarrow Y$ be a surjective morphism between normal projective varieties. Let $D$ be a $\mathbb{Q}$-divisor on $Y$. If $f^*D$ is semi-ample, so is $D$.
It is part of the content of Lemma 3.6 in these notes:
http://math.mit.edu/~mckernan/Teaching/07-08/Autumn/18.735/l_3.pdf
I would just like to have a more formal reference to include in my bibliography, like a book or a paper.