With online delivery increasingly dominating scientific publishing, most long-established journals run papers in both print and online formats — but not necessarily simultaneously. This can affect how researchers are given scientific priority. In our view, scholars from all disciplines should use the earlier, online citation date, rather than defaulting to print as the traditional record.
In our experience, the time lag between the two can be as long as 6 months. This might be crucial for annual research evaluations, for instance, when a paper is published online at the end of one year and in print the year after (see, for example, A. L. Woerman et al. Acta Neuropathol. 135, 49–63; 2018, originally published online in August 2017). Timings are also key when two competing groups publish papers that report similar findings. Young scientists, in particular, need to have the publication date of their original work accurately recorded.
Using the online publication date as the primary citation would dispel such confusion. Reference lists that include dates for both publication formats and are picked up by public databases such as PubMed are a step in the right direction. Editors, authors and indexers need to work together to manage any effect on priority when publishing a paper in both formats.
Nature 558, 519 (2018)