Additional file 2: Text S1

•	Pubmed (http://www.ncbi.nlm.nih.gov/pubmed)
•	Web of Science (http://ipscience.thomsonreuters.com/product/web-of-science/) 
•	OpenGrey (http://www.opengrey.eu/)
•	OAIster (http://oaister.worldcat.org/)
•	CABDirect (http://www.cabdirect.org/)
•	Japan; J-stage (https://www.jstage.jst.go.jp/browse)
•	Journals online, Asia (http://asiajol.info/)
•	WHO IRIS: (http://apps.who.int/iris/)
•	Index Medicus for South-East Asian Region: (http://imsear.hellis.org/)
•	China National Knowledge Infrastructure: (http://en.cnki.com.cn/)
•	Western Pacific Region Index Medicus (WPRIM): (http://www.wprim.org/)
•	Registry of Open Access repositories (http://roar.eprints.org/cgi/search/advanced)
•	TIM2(http://openaccess.xyz/search.php)
•	OpenDOAR (http://www.opendoar.org)
•	USDA National Agriculture Library (http://agricola.nal.usda.gov/)
•	Networked Digital Library of Theses and Dissertations (NDLTD) (http://www.ndltd.org/)
•	British Library E-thesis online service (http://ethos.bl.uk/Home.do;jsessionid=ADD34566923B6F193366A61D8D009239)
•	Swedish University Dissertations (http://www.dissertations.se/)
•	Spanish PhD Thesis (https://www.educacion.gob.es/teseo/irGestionarConsulta.do;jsessionid=2DA8162C9E0FF872824BA69A64FB784A)
•	French Thesis Online (http://www.theses.fr/)
•	TesiOnline (Italy) (http://www.tesionline.com/intl/index.jsp
•	German National Library (http://www.dnb.de/EN/Home/home_node.html)
•	Thesis Canada (http://amicus.collectionscanada.gc.ca/thesescanada-bin/Main/AdvSearch?coll=18&l=0&v=1)
•	Australasia Digital Theses Program (http://adt.caul.edu.au/)
•	Center for Research Libraries (http://catalog.crl.edu/search~S4)