Dear Physics Forum friends, I am a college junior who is currently conducting the undergraduate research in the theoretical computer science. I wrote this post to seek you recommendation on the books that separately treat the graph theory and combinatotics, both in theory and applications. I really need to understand the graph theory and combinatotics as it is one of the crucial parts of my current project. I am encountering terms like counting problems, matchings, H-coloring/homomorphisms, 2-3 graphs, etc. I am currently taking Analysis I (Rudin) and Linear Algebra (Hoffman/Kunze) so I have a good degree of mathematical maturity, but I would like books that treat the combinatorics and graph theory in a reader-friendly, introductory levels.