While [Unable to write template] is LaTeX markup, [Unable to write template] involves lower-level TeX structures. The former can easily be redefined to suit the book's layout.
A basic system for doing replacements has been completed. It should be adjusted slightly to keep things really consistent.
Use
\begin{oldbracketdisplay}...\end{oldbracketdisplay};to replace old brackets (used innocently enough by PM authors), and
\begin{doubledollars}...\end{doubledollars};to replace all double dollars (these can then be adjusted later).
Realize also that [Unable to write template] should we avoided when working with LaTeX. As it was mentioned, this is plain TeX, and causes vertical spacing inside the formula to become inconsistent, breaks fleqn option for amsmath. The proper way is to use [Unable to write template] or \begin{displaymath}…\end{displaymath}
More references: [l2tabuen – An essential guide to LaTeX2e usage] ( http://www.tug.org/teTeX/tetex-texmfdist/doc/latex/general/l2tabuen.pdf ) under the Deadly sins section. --drini
Some changes will have to be put into the PM style guide to get authors to agree to use the "correct" mark up (and to make FEM-originating corrections kosher).