I am writing a review article and have come across a number of references which were published verbatim in their entirety in more than one place ([Duplicate Publications](https://en.wikipedia.org/wiki/Duplicate_publication)). All of the publications in question are before 1970 and may be divided into two classes: those that have an instance with a statement that the content has been published or presented elsewhere (which references the duplicate) and those lacking such a statement. For those with a statement, I am inclined to cite the earliest instance and omit the later. However, the approach is unclear for those where precedence is not apparent. **I am looking for any recommendations (best practices, examples) on how citing duplicate publications should be handled in general.** I have not come across an example in my literature review and have been unable to find any guidance (most search results are related to *preventing* duplicate publications rather than coping with their aftermath decades later). Options I see at the moment (some of which are more palatable than others): 1. Don't explicitly acknowledge the duplication, but cite both variants in the text and bibliography (i.e., a parenthetical or textual citation with *both* instances each and every time I want to reference its/their content). 2. Pick one (randomly if precedence cannot be determined) and ignore the other. 3. Pick one (randomly if precedence cannot be determined) and include a footnote at the first use indicating that another instance exists (the alternative instance would be cited there with the full citation included in the cited references section). 4. Pick one (randomly if precedence cannot be determined) and modify the full citation in the cited references section to indicate that another instance exists and provide the full citation of the alternative. Some additional, possibly relevant information: - Subsequent publications are inconsistent in which instance is cited (i.e., both are cited and precedence is often ignored). - The field is environmental biotechnology.