Appraisal of: Greenhalgh T, Peacock R. Effectiveness and efficiency of search methods in systematic reviews of complex evidence: audit of primary sources. BMJ 2005; 331(7524): 1064-1065.
To describe where papers come from in a systematic review of complex evidence. Only 30% of sources were obtained from the protocol defined at the outset of the study (that is, from the database and hand searches). Fifty one per cent were identified by “snowballing” (such as scanning reference lists (44%) and citation tracking (7%)), and 24% by personal knowledge or personal contacts.