One excellent resource is the ebook, Nursing Theorists and Their Work by Martha Raile Alligood. This ebook supports 3 simultaneous users and can be accessed at the link below. If not available, try the older edition which is nearly the same and also supports 3 users at one time. 

We have many print books in our collection either about or by different nurse theorists. Use the library catalog to find those resources. 

One can also search for articles about nursing theories or nurse theorists by using subject headings or keywords in the search boxes. CINAHL would be the best individual database option or SuperSearch to conduct a search in all databases simultaneously. To look for articles or books written by the nurse theorist, use that person's name as an author in a search (ex: Orem, Dorothea or Mercer, RT). Contact a librarian or schedule a RAP session for additional assistance.