This document discusses the importance and sources of literature reviews. It defines a literature review as aiming to comprehensively review knowledge on a research topic. Literature reviews provide guidance on a topic, help identify research gaps and questions, and inform methodology. Primary sources directly report original research, while secondary sources summarize and interpret prior work. Relevant literature can be searched through electronic databases, journals, books and more. A good literature review is comprehensive, up-to-date, systematic, unbiased, and clearly organized with an introduction, body, and conclusion.