HEVEA amsmath package defines some of the constructs of the
amsmath package. At the moment, supported constructs are
the cases environment and matrix
environments [LATEX-bis, Section 8.4], the
environments for multi-line displayed
equations (gather,
split,...) [LATEX-bis, Section 8.5] and the
\numberwithin command [LATEX-bis, Section 8.6.2].