Since MAG topics will stop being produced after 12/31/2021, we should consider another topic taxonomy.
CORE has their own 'topics'
Semantic Scholar has top-level 'fieldsOfStudy' from MAG or Mesh? Also they have their own 'topics', but don't seem as accurate or as comprehensive as MAGs.
Dimensions.ai's "fields of research"
Crossref's "subjects" from Scopus. Subjects are manually assigned to journals not individual papers. https://service.elsevier.com/app/answers/detail/a_id/15181/supporthub/scopus/
Since MAG topics will stop being produced after 12/31/2021, we should consider another topic taxonomy.
CORE has their own 'topics' Semantic Scholar has top-level 'fieldsOfStudy' from MAG or Mesh? Also they have their own 'topics', but don't seem as accurate or as comprehensive as MAGs. Dimensions.ai's "fields of research" Crossref's "subjects" from Scopus. Subjects are manually assigned to journals not individual papers. https://service.elsevier.com/app/answers/detail/a_id/15181/supporthub/scopus/
https://github.com/Crossref/rest-api-doc/blob/master/api_format.md
crossref has about 113,000,000 articles. It contains references, and venue.