MathJax ref problem

MathJax \ref doesn't work for the split equation

by Brett

HTML

<script src="https://cdn.mathjax.org/mathjax/latest/MathJax.js?config=TeX-AMS_HTML"></script>
\begin{equation}
    \label{eq:foo}
    i^2=j^2=k^2=ijk=-1
\end{equation}

\begin{equation}
    \label{eq:bar}
    \begin{split}
        q_1q_2= & (a_1a_2-b_1b_2-c_1c_2-d_1d_2) \\
        + & (a_1b_2+b_1a_2+c_1d_2-d_1c_2)i \\
        + & (a_1c_2-b_1d_2+c_1a_2+d_1b_2)j \\
        + & (a_1d_2+b_1c_2-c_1b_2+d_1a_2)k
    \end{split}
\end{equation}

<p>Equation \ref{eq:foo}</p>
<p>Equation \ref{eq:bar}</p>

JavaScript

MathJax.Hub.Config({
  TeX: {
    equationNumbers: {autoNumber: "AMS"}
  }
});