The type and the number of sources you need for your literature review may vary depending on the purpose of your literature review (see below) and your level of study.
Therefore, you have to know very well the purpose and the type of your literature review.
The book "Crisis communication: Theory and practice" written by A. Zaremba provides an overview of the topic "crisis communication".
Another book "The handbook of crisis management" edited by W.
"In writing the literature review, the purpose is to explore what knowledge and ideas have been established on a topic, what approaches and viewpoints have been adopted, and what are their strengths and weaknesses." The requirements of narrative literature reviews are usually quite different than systematic reviews.
However, you may be required to adopt some of the characteristics of a systematic approach when doing your literature review.
A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question.
The key characteristics of a systematic review are: a clearly defined question with inclusion & exclusion criteria; rigorous & systematic search of the literature; critical appraisal of included studies; data extraction and management; analysis & interpretation of results; and report for publication.
Today it is the most common form of review in the humanities and parts of social sciences.
The important contribution of a narrative review is the author’s interpretation and critique of the literature under scrutiny in the review.