J. Friedrich, N. Adhikari, and J. Beyene. BMC medical research methodology, (January 2007)4704<m:linebreak></m:linebreak>LR: 20081120; JID: 100968545; OID: NLM: PMC1783664; 2006/11/14 received; 2007/01/23 accepted; 2007/01/23 aheadofprint; epublish;<m:linebreak></m:linebreak>Metaanàlisi.