References are becoming more and more important on Wikidata. Would be nice to track the number of (unique) references to indication on how well an item is sourced. This task is very similar to T114617

Let's take https://www.wikidata.org/wiki/Q50626475 . Looking at the rdf at https://www.wikidata.org/wiki/Special:EntityData/Q50626475.rdf the item has two references (same url, but different date of retrieved). That's also what https://query.wikidata.org/sparql?query=SELECT%20DISTINCT%20%3Fprovenance%20WHERE%20%7B%0A%20%20wd%3AQ50626475%20%3Fproperty%20%3Fstatement%20.%0A%20%20%3Fstatement%20prov%3AwasDerivedFrom%20%3Fprovenance%0A%20%20%7D%20LIMIT%20100%0A%20%20 returns. The field should contain 2 here for this item.

The name for the new page_prop should probably wb-references