A literature review is a systematic approach to finding, retrieving and analyzing published research on a specific topic or question.
A literature review is generally conducted at the beginning of a research project. If the project is ongoing over a long period of time, further searches may be necessary in order to include the latest published research.
The scope of the literature review depends on the research project. In general, a comprehensive literature review for an engineering research project typically includes journal articles and conference papers. It may also include technical reports, patents, theses and books.