A dissertation is a lengthy review of one subject or important problem. It is written as evidence of the writer's ability to think of a topic, perform extensive research, and write a clear assessment of his/her findings. The work generally incorporates previous research with new data and the interpretation of that data. It is often used to determine whether or not a student is qualified to receive an advanced degree.

 Writing up Research: Using the Literature
 The Dissertation  and Thesis Handbook