Books and ebooks are excellent at providing information on nursing theories and theorists. They typically provide background information and may include chapters devoted to specific theories. Books and e-books may also have extensive bibliographies with citations to a theorist's early works. Early works are helpful for understanding the origins of a theory.
When looking for books on a specific nursing theory or theorist, begin your search using the name of the theory or theorist.
Or, search more broadly to find books with chapters devoted to different nursing theories. Recommended search terms include: nurse theorists, nursing theory, middle range theory.
CINAHL is a good database for finding scholarly articles written by a nursing theorist or articles about their theories. This databases is available in Databases by Subject for Healthcare.