Scholarly/academic/peer-reviewed sources are sources written by experts and are reviewed by experts in the field before the article is published.
You may consider scholars with subject expertise have authority in the area of your research topic and thus produce only good sources. However, like all types of sources and authorities, scholarly sources vary a lot by date, scope, method, and etc, making only some of them appropriate to cite in your research. Scholarly sources may have totally valid evidence but not so relevant to your research.
Finding a good scholarly source to use can sometimes be a messy process, but below are some questions you can ask yourself in order to determine if the academic article is worth using in your research.
It is important to take into account the level accountability associated with different kinds of sources.
Popular sources are largely intended to entertain, but sometimes also to inform. However, the threshold of proof required to publish information in a popular source is relatively lower than academic sources.
Academic sources require peer review, which includes the approval of experts on the subject in order for publication to be improved.
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