https://en.wikipedia.org/wiki/Wikipedia:User_scripts/List#References_2
Add button to top of article that adds https://en.wikipedia.org/wiki/Template:Duplicated_citations ?
Is there a bot somewhere scanning for duplicate urls in refs?
perhaps also check duplicate dois and isbns, which resource identifiers(if that is the correct term) exist? ISSN/ISBN/doi/S2CID/OCLC
https://en.wikipedia.org/wiki/Category:All_articles_with_duplicate_citations
https://en.wikipedia.org/wiki/Template:Catalog_lookup_link#See_also