  In this paper, we continue our study of closed models defined in categories
of graphs. We construct a closed model defined in the cat-egory of directed
graphs which characterizes the strongly connected components. This last notion
has many applications, and it plays an important role in the web search
algorithm of Brin and Page, the foun-dation of the search engine Google. We
also show that for this closed model, Euler graphs are particular examples of
cofibrant objects. This enables us to interpret in this setting the classical
result of Euler which states that a directed graph is Euleurian if and only if
the in degree and the out degree of every of its nodes are equal. We also
provide a cohomological proof of this last result.
