How to rescale equations formatted using 'align'? Resizebox doesn't appear to work

Question

My question is similar to the one here as well as here, but for some reason the proposed solution i.e. use resizebox, doesn't work for me.

I know that the 'obvious' answer is to add more line breaks, but this doesn't really make sense for what I'm trying to do which is to print my thesis using as few pages as possible (for proof reading purposes).

Here is my MWE:

\documentclass[10pt, oneside, twocolumn, notitlepage]{book}
\usepackage{amsthm,latexsym,amssymb,amsmath, amsfonts}
\usepackage{graphicx}
\usepackage{lipsum}

\newtheorem{thm}{Theorem}[section]


\newtheorem{rem}[thm]{Remark}

\begin{document}
\lipsum[1]
%\resizebox{.9\linewidth}{!}{
\begin{align*}
\mathrm{Term_{2a}} &=\iint  \left[\nabla \phi_t(x) \cdot \nabla \phi(y) + \nabla \phi(x) \cdot \nabla \phi_t(y) \right]\  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
&=\iint  \nabla \phi_t(x) \cdot \nabla \phi(y)  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
\end{align*}%}
\lipsum
\end{document}

This is what it looks like:

Adding the resizebox{.9\linewidth}{!}{...} command produces the following errors (apologies it's rather small):

Answer 1

It seems that scalebox doesn't work well with math mode. A possible solution is to put your align inside a minipage:

\documentclass[10pt, oneside, twocolumn, notitlepage]{book}
\usepackage{amsthm,latexsym,amssymb,amsmath, amsfonts}
\usepackage{graphicx}
\usepackage{lipsum}

\newtheorem{thm}{Theorem}[section]


\newtheorem{rem}[thm]{Remark}

\begin{document}
\lipsum[1]

\resizebox{.9\linewidth}{!}{
  \begin{minipage}{\linewidth}
  \begin{align*}
\mathrm{Term_{2a}} &=\iint  \left[\nabla \phi_t(x) \cdot \nabla \phi(y) + \nabla \phi(x) \cdot \nabla \phi_t(y) \right]\  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
&=\iint  \nabla \phi_t(x) \cdot \nabla \phi(y)  e^{-\frac{\|x-y\|^2}{d^2}} W_{l}(\phi(x))W_{l}(\phi(y)) \mathrm{\ dx \ dy} \\
\end{align*}
  \end{minipage}
}

\lipsum
\end{document}