== Erdős–Bacon number == 

 This edit: are you serious? To take a similar example: Natalie Portman says she was born in 1981 (for which there are no refs, but let's assume there are). It also says "(age 28)" in the infobox. Do you put a  on the "age 28"? No, because it follows logically from the birth date, and anyone can see that. I don't see why you insist that a citation is needed for the fact that for  to be well-defined, it is necessary for one to have both appeared in a film and co-authored an academic paper. It follows logically from the definition. We only put  on things that could possibly be false. I don't understand what your intention is.