• latex-amsmath, which provides miscellaneous enhancements to LaTeX to improve the appearance and information structure of mathematical documents, and
• amscls, which offers document classes designed for preparing articles and books for publication by the American Mathematical Society (though they are often used in other contexts).

See also amsmath amscd amstext amsart amsbook amsproc amsrefs amsthm.

The author is The American Mathematical Society.