Powell S, Forslund K, Szklarczyk D, Trachana K, Roth A, Huerta-Cepas J, Gabaldón T, Rattei T, Creevey C, Kuhn M, Jensen LJ, von Mering C, Bork P. (2014) eggNOG v4.0: nested orthology inference across 3686 organisms. Nucleic Acids Res. 42(1):D231-9.