\documentclass[reqno]{amsart} \usepackage{amsfonts} \usepackage{amssymb} \usepackage[T1]{fontenc} \usepackage{ae} \usepackage{hyperref} \numberwithin{equation}{subsection} \begin{document} \section{My section title} Some text. \subsection{My first subsection} \label{ss:first} \begin{equation} \label{eq:A} p^{\prime\prime} + \dfrac{S^\prime}{S}p^\prime +k^2p = 0 \end{equation} Let's refer to equations~\ref{eqs:C} in subsection\ref{ss:second}. \begin{equation} \label{eq:B} g(x)=const \times f(x) \int^{x} \dfrac{d\xi}{S(\xi)f^{2}(\xi)} . \end{equation} Now I'll force a new page so the hyper-references will bridge a page boundary. \newpage \subsection{My second subsection} \label{ss:second} Now some subequations. \begin{subequations} \label{eqs:C} \begin{align} p^\prime& = -Z(x)U \label{eq:pC} \\ U^\prime & = -Y(x)p \label{eq:UC} \end{align} \end{subequations} These are related to equation~\ref{eq:A} in subsection~\ref{ss:first}. {% \begin{subequations} \label{eqs:D} \begin{align} p^\prime& = -j \omega {\dfrac{\rho}{S(x)}}U = -jk {\dfrac{\rho c}{S(x)}}U \label{eq:pD} \\ U^\prime & = -j \omega {\dfrac{S(x)}{\rho c^{2}}}p = -jk {\dfrac{S(x)}{\rho c}}p \label{eq:UD} \end{align} \end{subequations} } \end{document}