Mihaela Pertea Kunmi Ayanbule Megan Smedinghoff Steven L. Salzberg OperonDB: a comprehensive database of predicted operons in microbial genomes. 479-482 2009 37 Nucleic Acids Research Database-Issue http://dx.doi.org/10.1093/nar/gkn784 db/journals/nar/nar37.html#PerteaASS09