CrossRef
MIT Library
Washington State University Library
Ulrich's update
Socolar
Google Scholar
Index Copernicus
Tornto Public Library
Genamics
Microsoft Academic Search
OpenJ Gate
ISC
Scirus
DOAJ
AMICOS
ProQuest
Tamkang University of Taiwan
EBSCO
University of GeorgeTown
University of Strathclyde Library
University of Tohoku Library
Indiana University Library
University of North Dakota Library
NovaNet
York University of Canada
University of Tsukuba
University of Tatung