(related variations: sxm stm)

A StarOffice (version 6 and later) or OpenOffice math document (they are the same); can be read on any machine with StarOffice or OpenOffice installed (available for free for many platforms including WinTel boxes, Macs, and some types of UNIX boxes). The version with the "x" is an ordinary document; the version with the "t" is a template for building other documents.