1. Improving the quality of reports of meta-analyses of randomized controlled trials: the QUOROM statement;Moher;Lancet,1999
2. InterTASC Information Specialists' Sub-GroupSearch filter resource. Available at http://www.york.ac.uk/inst/crd/intertasc/rct.htm Accessed May 5, 2008.
3. Cochrane handbook. Available at http://www.cochrane.org/admin/manual.htm Accessed November 2007.
4. Systematic reviews in the social sciences: a practical guide;Petticrew,2005
5. The ethics of early stopping rules;Pater;J Clin Oncol,2005