TITLE: Graph theory resource for mathematical Olympiads
QUESTION [7 upvotes]: I would like to learn a bit of Graph theory for mathematical Olympiads.Can anyone please point out a resource from where I can learn it? Here's my background: I have limited knowledge of linear algebra but I know basic combinatorics including counting, pigeonhole principle, bijection, recursion, counting in two ways etc.I do not mind an elementary but really tough 
introductory book/resource.Thanks a lot in advance.

REPLY [2 votes]: Part 3 of Discrete and Combinatorial Mathematics, An Applied Introduction by Ralph P.Grimaldi (4th editon): "Graph theory and applications".