When I run
\documentclass{article}
\usepackage{simpler-wick}
\usepackage{amsmath}
\begin{document}
\begin{equation}
\begin{split}
x &= \wick{\c a \c b}\\
x &= y\\
\end{split}
\end{equation}
\end{document}
then the output looks just fine, except that I repeatedly get warning messages
LaTeX Warning: Reference `refmathstyle@1' on page 1 undefined on input line 9.
LaTeX Warning: Reference `refmathstyle@2' on page 1 undefined on input line 9.
These warning messages go away if I remove the 'split' environment. Is there a way to get rid of these warning messages in a split environment?
LaTeX,pdfLaTeXandXeLaTeXof texlive and could not get your warnings... Possibly some more info like yourlogfile is needed here. – koleygr Mar 14 '19 at 15:37