Theorem (Triangle-free Lemma). For all $\eta>0$ there exists $c > 0$ and $n_0$ so that every graph $G$ on $n>n_0$ vertices, which contains at most $cn^3$ triangles can be made triangle free by removing at most $\eta\binom{n}{2}$ edges.

I am trying to find some information related to this topic, I am unable to access the orignal paper by Ruzsa & Szemeredi.

Does anyone know any useful papers/books on the triangle-free lemma?