... We searched 30 electronic databases from January 1980 to February 2007: ADOLEC, AIDSLINE, AMED, ASSIA, BiblioMap, BIOSIS, BNI, Catalog of US Government Publications, CENTRAL, CHID, CINAHL, DARE, Dissertation Abstracts International, Embase,...
http://www.bmj.com/cgi/content/full/335/7613/248