Stanley Letovsky Robert W. Cottingham Christopher J. Porter Peter W. D. Li 94-99 1998 26 Nucleic Acids Res. 1 db/journals/nar/nar26.html#LetovskyCPL98 https://doi.org/10.1093/nar/26.1.94 https://www.wikidata.org/entity/Q24545845