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Usefulness of contacting other experts when conducting literature searches

Editor—McManus et al described the usefulness of hand searching and contacting other experts when conducting a literature search.1 The eight authors were all contributors, and one of them acted as guarantor.1 
 
As occasional authors of systematic reviews we were particularly interested in the assertion that “electronic databases, such as Medline, may detect only about half of papers identified by the gold standard of hand searching journals.” We read the paper cited as the reference for this information. It was another BMJ article.2 We could not, however, find the original data suggesting that hand searching is a gold standard, or that electronic databases find only half of relevant papers. Reference was made to another work. Whether this was the original source of data is still unclear to us, since the reference was not an to article or even an abstract but to a communication presented at a workshop held in March 1992. 
 
McManus et al’s short paper was on medical publication and was published in a leading journal in this field. A major reference regarding the background and the results of the study was the secondary citation of a paper reported at a workshop six years before. Papers reported at meetings should be cited only in the text, not as formal references,3 and secondary citations should be identified. If a work unpublished several years after oral presentation deserves mention it should be presented unambiguously to readers. 
 
Only a fraction of readers can afford to spend time scrutinising the literature cited and to check the validity of references. Whether this should be done by the editor, the referees, the contributors, or the guarantor can be debated.