I am the lead author on a journal paper to the IEEE, and I'm trying to figure out how to cite other contributors in a way that makes sense. Two of us are affiliated with a university, one contributor is a wonderful and knowledgable mathematician whose "real job" is in the service industry, and the other contributor is also a math nerd who is a barista in another country that did all of the proofs.
Would these non-conventional authors be "independent" or "unaffiliated" or some other term. The affiliation is required by the journal. Any suggestions (or a definitive source) of how to handle this issue would be appreciated.