Bielefeld Academic Search Engine (BASE) - https://www.base-search.net/

CiteSeerX - http://citeseerx.ist.psu.edu/index

EconBiz - http://www.econbiz.de/

EKUAL Keşif - https://cabim.ulakbim.gov.tr/ekual/

Google Scholar (Akademik) - https://scholar.google.com.tr/

Hathi Trust Digital Library - https://www.hathitrust.org/

Refseek* - http://www.refseek.com/