In computing, AAP DTD (variously known as AAP Electronic Manuscript Standard, AAP standard, AAP/EPSIG standard, and ANSI/NISO Z39.59) is a set of three SGML Document Type Definitions (book, journal, and article) for scientific documents, defined by the Association of American Publishers. It was ratified as a U.S. standard under the name ANSI/NISO Z39.59 in 1988, and evolved into the international ISO 12083 standard in 1993. It was supplanted as a U.S. standard by ANSI/ISO 12083 in 1995.