zbMATH Open (formerly known as Zentralblatt MATH) is the world's most comprehensive and longest-running abstracting and reviewing service in pure and applied mathematics. It is edited by the European Mathematical Society (EMS), the Heidelberg Academy of Sciences and Humanities, and FIZ Karlsruhe.
The Lean mathematical library, mathlib, is a community-driven effort to build a unified library of mathematics formalized in the Lean proof assistant. The library also contains definitions useful for programming.
Single click access to library content from publisher websites, PubMed, Wikipedia, and more; link to the full range of available content, including primary publishers, aggregators, open access alternatives; easily install in Chrome, Firefox, Edge, Vivaldi, or Brave.