I am recently coming across a lot of questions relating to graph theory, one of them is the following:
Given a simple graph G with n vertices. One edge e of G is called edgy, if the vertices of G can be split up into to subtotals A and B such that there are at most 100 edges with one end in A and one end in B and one of these is e. Prove that G has at most 100n edgy edges.
I looked for graph theory books on google and these books came up:
I am looking for books containing graph theory used in IMO's, so that I can learn the theory required for such questions. Could you please suggest some books?