Literature reviews are common in most social scientific and scientific disciplines. They essentially summarize the previous research that has been done on a particular issue, pointing out agreements and disagreements as well as indicating where further study is needed. 

(In the following videos, please excuse the annoying ads.)

For a short video on the literature review 

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For a longer but very informative explanation, see the two brilliant videos by "Smart Student."

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(Open to full screen. If the video does not load, go to https://youtu.be/ki0JCQLepgo)

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(Open to full screen. If the video does not load, go to https://youtu.be/DMsdY5Z5bZk)