Final answer:
Biographical resources are the most appropriate source to consult when seeking information on specific individuals or groups, due to their comprehensive and specialized nature.
Step-by-step explanation:
When looking for information about a specific individual or groups of individuals, the most appropriate resource to consult would be Biographical resources. Biographical dictionaries, in particular, are compiled to provide information about people who have made notable contributions to various fields. Some key biographical references include Contemporary Authors, which offers short biographies of authors who have published within the year, Current Biography for articles and photographs of newsworthy individuals, and Who's Who in America, a standard reference for biographical data on living Americans. While encyclopedias and textbooks provide a broad range of general knowledge, including some biographical information, they are not as specialized as biographical resources. Periodical publications could also contain relevant biographical information, particularly in articles featuring individuals, but they may not be as comprehensive as dedicated biographical sources.