Google Scholar, Journal TOCS,  CrossRef, BASE, Semantic Scholar, DRJI, Research Bib, Genamics, PKP Index,  Root Indexing, Cosmos,  International Institute of Organized Research (I2OR), Scribd, Scientific Indexing Services (SIS), Worldcat, Beißen Gedanken, Research Gate, Journal Informatics, Open J-Gate, Elektronische Zeitschriftenbibliothek, International Scientific Indexing, Publons,  Katalog fur die Bibiliotheken der Universitat Heidelberg, Eurasian Scientific Journal Index(ESJI), SHERPA/ROMEO, etc.