# Create link to the top of a page which contains a certain labelled object

I want to create a clickable link from which I can jump to the top of the page which contains a certain labelled object. I tried \pageref but then clicking on the corresponding link results in a jump to the exact site of the labelled object [formula (1) in the MWE below]. Instead, I want to jump to the top of the corresponding page [top of page 2 in the MWE below]. Is that possible?

\documentclass{article}
\usepackage{lipsum}
\usepackage{hyperref}
\begin{document}
\lipsum
$$\label{a} a:=b$$
\lipsum
Note that $a$ is defined in (\ref{a}) on page \pageref{a}.
\end{document}

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Here's one approach if hyperref option hypertexnames is set (it is by default):

\documentclass{article}
\usepackage{lipsum}
\usepackage{hyperref}
\usepackage{refcount}
$$\label{a} a:=b$$
Note that $a$ is defined in (\ref{a}) on page \pagereftop{a}.