WikiProvenance: Are there enough references to every (known) fact on Wikidata?

In a collaborative website like Wikidata, contributors add statements about an item like a person, a scientific subject, a historical place etc. Each of these statements need to be backed by a reference.
Yet a large number of statements are added without references. Even well-described items (i.e., the items with a lot of statements) like Douglas Adams, Albert Einstein do not have references on all these facts. During the past few years, there has been a lot of focus on increasing the number of statements of items usually referred to as the item completion efforts. Yet, the references to statements cannot be undermined. That being said, it is equally important to understand the use of external identifiers and links to existing multilingual Wikimedia projects for these items. Since many of these sources also contain a large number of references. Both contributors and users need to get an overview on the reference statistics. With WikiProvenance, the goal is to understand and delve into details of the usage of references, the links to external sources in an open and transparent manner.