Can apply to: Scholarly monographs and trade books, and chapters of scholarly monographs
Metric definition: The number of times that a book or chapter has appeared in the reference list of other articles and books.
Metric calculation: Many citation databases use a combination of text-mining and manual classification to build their lists of citations. However, the scope of these databases varies, with some databases indexing citations to far fewer books than others.
Data sources: Book Citation Index (available through Web of Science), Google Books, Google Scholar, Scopus
Appropriate use cases: As with journal articles, there are many, many reasons why scholars cite each others’ work, so it’s impossible to say that there is one way that citations should be interpreted. The closest one can get is to say that citations are a measure of influence amongst other scholars, and that influence can sometimes be negative (especially in the humanities).
Limitations: One needs to read the context of a citation to understand its true meaning. In general, it is more difficult to find comprehensive citations to a monograph or to its chapters than for a journal article, due to the limited scope of major book citation databases. The current means of calculating citations (tracking a monograph’s appearance in a reference list) do not account for how often a monograph is cited in another text. For example, some works are cited many times throughout a text and are thus central to another scholars’ research, while other works are cited only once. Most citation databases that include books share the limitations of other citation databases: they favor English-language research and newer monographs, missing local and regional research published in other languages, as well as older monographs.
Inappropriate use cases: Citations should never be interpreted to directly measure quality. Raw citation counts should not be used as a measure of positive esteem for researchers.
Available metric sources: see Data sources, above
Transparency: Citations are only as transparent as the availability of the citing article or book allows them to be. One may not always be able to read citations in context, given the prevalence of subscription journals to which reviewers are not guaranteed access. Most databases that report citations report the full list of citing articles and books, at the very least, linking through to full-text articles and books where possible (even if only for subscribing institutions).
Timeframe: In theory, it is possible to track citations to books published hundreds of years ago. But in practice, most databases only track citations for books published in the 20th century and beyond.