Remember that sources not specifically on your topic can still provide relevant related information. Read abstracts of the publication, or scan introductions, tables of contents, and indexes for a quick overview of its contents. Even repetition of what you have already turned up in your research can help to confirm or deny the accuracy of those findings. Who's Who in America , Biography Index , and other biographical reference sources. You can also check a Citation Index to see whether other scholars have cited this author in their publications.
Books can provide broad and thorough coverage of a range of related topics.
Journal articles are more narrowly focused, but can be published quickly to provide more up to date information. Audio and visual recordings, diaries, letters, business records, lab reports, and many other sources, published or unpublished, can offer useful information depending on your research needs. Think very broadly about the possibilities for sources for your research. Knowledge in the sciences develops and accumulates very quickly, and scientific research requires current information. Humanities research is not as time-sensitive.