DOAJ
DBLP
CrossRef
EBSCO Discovery Service
EBSCO Essentials
OCLC Discovery Services
EuroPub
Publons
MIAR
Microsoft Academic Search
Dimensions
UlrichsWEB
Hellenic Academic Libraries Link
Ingenta Connect
Publicly Available Content Database (ProQuest)
Advanced Technologies & Aerospace Database (ProQuest)
SciTech Premium Collection (ProQuest)
Google Scholar
