Where did this come from? When (not how) to cite sources in scientific publications

In the scientific literature, the link between an idea and its source is its reference information that allows the source to be identified and located. Not so obvious is where the source is cited in the text. Although authors are given extensive details on how to format references, they are not always taught when to cite them. Further, many are not vigilant in confirming the accuracy of the quoted information against the source or in verifying the associated reference information. In fact, discrepancies between the information cited in the text and the information actually presented in the source are common and often serious. Further, inaccuracies in references that break the link between the citation and its source are even more common. These discrepancies and inaccuracies affect the integrity of science and the validity of the citation metrics (for example, the Journal Impact Factor) that are used, rightly or wrongly, to evaluate the importance of journals and authors. Here, I discuss factors affecting when and where sources should be cited. I also consider factors that can bias the selection of sources and so interfere with the validity of citation analyses, review some considerations for evaluating a source, call attention to citation and quotation error rates, and review some strategies for reducing these errors. Finally, I summarise the most common recommendations for when, what, where, and why sources should or should not be cited.