https://pmc-ref.herokuapp.com/
A quick way to check if an article's references are free to access in PubMed Central.
Given a digital object identifier (doi) pmc-ref will return the percentage of an article's references that are free to access in PubMed Central. It can also return the details of the references that are free to acess. There's also an API https://pmc-ref.herokuapp.com/api.
For researchers who would like freely accessible research.
If you'd like to contribute to this project please read more on the CONTRIBUTING.md