A number of books (e.g. enwikisource:The Nether World) are giving this epubcheck error:
Line 3 column 1582 of OPS/c0_The_Nether_World.xhtml: Error while parsing file: element "link" missing required attribute "property"
2: <!DOCTYPE html>
3: <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" dir="ltr"><head><meta content="application/xhtml+xml;charset=UTF-8" http-equiv="default-style"/><link type="text/css" rel="stylesheet" href="main.css"/><title>The Nether World</title><style><![CDATA[.mw-parser-output .__toc_table{border-collapse:collapse;background-color:transparent;margin:auto}.mw-parser-output .__toc_table td{vertical-align:top}.mw-parser-output .__toc_row_1-m-1 td:nth-child(1),.mw-parser-output .__toc_row_1-1-m-1 td:nth-child(1),.mw-parser-output .__toc_row_1-1-m-1 td:nth-child(2){text-align:right;white-space:nowrap;padding-right:1em}.mw-parser-output .__toc_row_1-m-1 td:nth-child(2),.mw-parser-output .__toc_row_m-1 td:nth-child(1),.mw-parser-output .__toc_row_1-1-m-1 td:nth-child(3){width:99%}.mw-parser-output .__toc_row_1-m-1 td:last-child,.mw-parser-output .__toc_row_1-1-m-1 td:last-child,.mw-parser-output .__toc_row_m-1 td:last-child{vertical-align:bottom;text-align:right;padding-left:1em;white-space:nowrap}.mw-parser-output .__toc_row_2out-1 td:nth-child(1),.mw-parser-output .__toc_row_1-out-1 td:nth-child(2){text-indent:-1.50em;padding-left:1.50em}.mw-parser-output .__no_first_col_padding td:nth-child(1){padding-right:0}.mw-parser-output .__no_last_col_padding td:last-child{padding-left:0}]]></style><style/><style/></head><body id="mwAA" class="mw-content-ltr sitedir-ltr ltr mw-body-content parsoid-body mediawiki mw-parser-output" dir="ltr" xml:lang="en"><section data-mw-section-id="0" id="mwAQ"><link typeof="mw:Extension/indicator mw:Transclusion" about="#mwt1" id="mwAg"/><meta property="mw:PageProp/categorydefaultsort" content="Nether World, The" id="mwAw"/>
4:The link is <link typeof="mw:Extension/indicator mw:Transclusion" about="#mwt1" id="mwAg"/>
Another example is <link typeof="mw:Extension/section" about="#mwt29" id="mwBQ"/> from Line 3 column 4696 of OPS/c0_Divina_Commedia.xhtml in itwikisource:Divina_Commedia.
Could we drop all <link> elements where typeof starts with mw:Extension?