For R33, the link goes on to list and explain the other usage rules for et al.
Using et al. in APA Style APA Style has slightly different rules for using “et al.” depending on whether you’re following the 6th or 7th edition.
7th edition rules In APA 7 in-text citations, when a source has two authors, list both. When there are three or more authors, cite the first author followed by “et al.”
“Et al.” in APA 7 Number of authors In-text citation 1–2 authors (Anderson & Singh, 2018) 3+ authors (McDonnell et al., 2019) Don’t use “et al.” in the reference list. Instead, list up to 20 authors in full. When a source has more than 20 authors, list the first 19, then an ellipsis (…), then the final name:
Example: APA reference entry with 21+ authors McDonnell, F., Davidson, M., Singh, J., Clobus, R., Davies, R., Eliot, A., McCombes, S., Caulfield, J., Streefkerk, R., Corrieri, L., LaBrode, M., Theel, M., Swaen, B., Debret, J., Jonker, S., Driessen, K., Baldwin, I., Bevans, R., Bhandari, P., … Peters, H.