★ CAS Source Index (CASSI), USA
★ Louisiana State University, LSU Libraries, USA
★ Anderson University Nicholson Library, USA
★ Scite Index
★ CrossRef
★ Google Scholar
★ WorldCat
★ BASE (Bielefeld Academic Search Engine), Germany
★ Harvard Library E-Journals, USA
★ SciLit, Switzerland
★ J-Gate
★ Semantic Scholar
★ Academia.edu
★ ROAD
★ Open Academic Journals Index (OAJI), USA
★ Scientific Indexing Services, USA
★ Turkish Education Index, Turkey
★ ScienceGate
★ ResearchBib
★ Zeitschriftendatenbank (ZDB)
★ Technische Informationsbibliothek (TIB)
★ PubScholar
★ Chinese Scientific Journals Database, VIP Corporation, Chongqing, China
★ WebQualis/SiCapes index, Brazil
★ Elektronische Zeitschriftenbibliothek EZB, Germany
★ DTU Findit
★ The Library of Congress
★ American Federal Computer Library Center (OCLC), USA
★ Chinese Database of CEPS
★ Index Copernicus, Poland 
★ China National Knowledge Infrastructure (CNKI), China