When you're planning your disseration, you need to review existing dissertations, as well as the disciplinary literature, to find out what's been researched on your topic.  It's also helpful to see examples of dissertations as you begin to write your own.  Here are a few sources to consult:

Writing your dissertation can be a long and at times difficult process.  To find a list of books on writing and completing a dissertation, use PittCat’s Advanced Search to search the following as Subjects:

• Dissertations, Academic -- Handbooks, manuals, etc
• Dissertations, Academic

Here are a few selected titles: