Library and Archives Service
LibKey Nomad works on over 1000 publisher sites, including:
•ACM Digital Library
•American Chemical Society (ACS)
•American Medical Association (AMA)
•American Psychological Association (APA)
•BMJ Publishing Group
•Cambridge University Press
•Elsevier Science (Science Direct)
•Oxford University Press
•Taylor and Francis
It also checks the citations on Wikipedia pages.
For the full list of supported publishers see the following page: What publishers do you support?