According to CSL spec 1.0.2, page is a number variable.

number-of-volumes
Total number of volumes, used when citing multi-volume books and such
page
Range of pages the item (e.g. a journal article) covers in a container (e.g. a journal issue)
page-first
First page of the range of pages the item (e.g. a journal article) covers in a container (e.g. a journal issue)

But somehow, it's missing in citationberg::taxonomy::NumberVariable.

Background

This issue blocks typst from loading 历史研究.csl.

https://github.com/zotero-chinese/styles/blob/85f17a42a9ec599397f0889ce3f161ae253b034b/src/%E5%8E%86%E5%8F%B2%E7%A0%94%E7%A9%B6/%E5%8E%86%E5%8F%B2%E7%A0%94%E7%A9%B6.csl#L532

<number variable="page"/>

Failed to load CSL style (unknown variant page, expected one of chapter-number, citation-number, collection-number, edition, first-reference-note-number, issue, locator, number, number-of-pages, number-of-volumes, page-first, part-number, printing, printing-number, section, supplement-number, version, volume)