Database	Time	Search Strategy
EMBASE	1980 ‐ 2007 week 28	1 selenium/ or selen$.mp. 2 exp Selenium Derivative/ 3 methylseleninic acid/ or methylselenium.mp. 4 exp Organoselenium Derivative/ 5 exp Clinical Study/ 6 exp NEOPLASM/ 7 Selenium 75/ 8 1 or 2 or 3 or 4 9 8 and 5 and 6 10 9 not 7 11 limit 10 to human
SIGLE [www.fiz‐informationsdienste.de] [the database was discontinued]	October 2004	?selen? with restriction to subject group "06 Biological and Medical Sciences (without Botanics, Zoology, Biophysics)"
Cancerlit	July 2007	1 random* OR placebo* OR clinical trial* OR randomized controlled trial* OR controlled clinical trial* OR double blind OR single blind 2 selen* OR organoselen* 3 1 AND 2
Clinical Contents in Medicine CCMed	October 2004	selen* OR organoselen* OR natriumselen*
NCI Clinical Trials [www.cancer.gov]	October 2004	medication=selenium
ISRCTN and mRCT [www.controlled‐trials.com]	October 2004	selenium AND cancer
German Register of Cancer Studies [www.studien.de]	July 2007	selen
Cochrane Pain, Palliative & Supportive Care Trials Register	July 2007	selen*
The Cochrane Database of Systematic Reviews; The Database of Abstracts of Reviews of Effects (DARE); The Cochrane Central Register of Controlled Trials (CENTRAL)	Issue 2, 2007	selen*