\samepage
The \samepage command still exists but is no longer being
maintained.
This is because it only ever worked erratically; it does not
guarantee that there will be no page-breaks within its scope; and
it can cause footnotes and marginals to be wrongly placed.
We recommend using \enlargethispage in conjunction with page-break
commands such as \newpage and \pagebreak to help control page
breaks.
\SLiTeX
Since SLiTeX no longer exists, the logo is no longer defined in the
LaTeX kernel. A suitable replacement is \textsc{Sli\TeX}. The
SLiTeX logo is defined in LaTeX 2.09 compatibility mode.
\mho \Join \Box \Diamond \leadsto
\sqsubset \sqsupset \lhd \unlhd \rhd \unrhd
These symbols are contained in the LaTeX symbol font, which was automatically loaded by LaTeX 2.09. However, TeX has room for only sixteen math font families; thus many users discovered that they ran out. Because of this, LaTeX does not load the LaTeX symbol font unless you use the latexsym package.
These symbols are also made available, using different fonts, by the amsfonts package, which also defines a large number of other symbols. It is supplied by the American Mathematical Society.
The latexsym package is loaded automatically in LaTeX 2.09 compatibility mode.