The reference counts in OpenAlex seem off. Why is that?

For each Work in OpenAlex, we have a field called referenced_works that is meant to list the works that were cited by that publication. The number of references included in OpenAlex for a particular work might be less than you observe in the PDF or even the Crossref record for that publication. There are a few reasons why that might be the case.

• for a work to be included in the referenced_works section, it must be a work that is in OpenAlex and so if one of the references isn’t indexed in OpenAlex, we won’t be able to include it in that section;
• sometimes the references included in the Crossref record for a publication differ from the reference section in the final PDF if references get added in production;
• often, references aren’t included in the Crossref record for a publication– in those situations, we try to get the references from the pdf directly, but parsing errors can happen and we can miss some of them;
• when we get reference information from Crossref or the PDF, we first try to match to OpenAlex works based on DOI (with high efficiency)– when DOIs aren’t included we try to match based on other metadata, but have less success in those situations.