The || 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 | in conjunction with page-break
commands such as || and || to help control page
breaks.
Since no longer exists, the logo is no longer defined in the
LATEX kernel. A suitable replacement is |SLITEX|. The
logo is defined in LATEX 2.09 compatibility mode.
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.