Which type of source is typically excluded from a literature review?

In a literature review, the type of source typically excluded is non-scholarly or non-peer-reviewed sources. These include documents and materials such as newspapers, magazines, blogs, online forums, testimonials, popular books, and any form of personal communication. The reason these sources are excluded is that they often lack the rigorous peer-review process that academic journal articles go through to ensure accuracy, reliability, and scholarly value.

Non-scholarly sources may also reflect bias, be outdated, or lack scientific validity. In contrast, scholarly sources, including peer-reviewed journal articles, books from academic publishers, and other high-quality academic writings, are preferred because they have undergone extensive scrutiny by experts in the field, ensuring their credibility and relevance to the topic being researched.