Do you notice anything unusual or potentially problematic that could be a red flag for a paper mill?

The diversity of affiliations and countries is one of the red flags of paper mills. This is a collaboration anomaly in which the authors’ areas of specialization do not correspond with each other or with the topic of the paper. Such a collaboration anomaly is not, by itself, a reason for correction or retraction, but it serves as a signal that a paper may originate from a paper mill.