In long-term projects, often a division of labor is necessitated. Some tasks may be delegated to helpers who perform relatively simple tasks, such as a student who goes to the laboratory and sits 4 hours per day monitoring an experiment run by the project author or an assistant who goes to libraries and gathers printed materials and screens them for topical relevance to the project without analyzing them. Single-author projects most often require the author to perform tasks such as these. Is there a set of criteria to help in determination of which project participants should be given published recognition as co-authors?