Reference tools such as dictionaries and encyclopedias are good places to start your research because they provide an overview of the topic as well as keywords, dates, and facts.
Historical Encyclopedia of Nursing
Ref. RT31 .S66 1999
Pivotal Moments in Nursing: Leaders who Changed the Path of a Profession
Ebook available here
American Nursing: A Biographical Dictionary
Ref. RT 34 A44
Tips: Try looking at the bibliography at the end of the entry for a list of other sources such as relevant journal articles and books. When you have found books on your topic, look at the books on the shelf nearby to see if they are related to your topic.