I need help writing a literature review. I have the 4 articles that need to be reviewed. The one I wrote is included in the attached files Two of the articles are written as PDF's in the uploads and t

I need help writing a literature review. I have the 4 articles that need to be reviewed. The one I wrote is included in the attached files Two of the articles are written as PDF's in the uploads and two are the links below. This is what the professor said about my original draft: In regards to your literature review - it would be beneficial to "pull" the references together vs. discussing each separately - please review the literature review formatting (-3). I'm not sure how to do what he is asking. 

The paper is a correlation about maintaining a healthy weight loss with a patient that has had surgical weight loss interventions and non-surgical weight loss (conventinal weight loss) 

http://www.psychiatrist.com/_layouts/PPP.Psych.Controls/ArticleViewer.ashx?ArticleURL=/pcc/article/Pages/2013/v15n05/12f01475.aspx

https://hqlo.biomedcentral.com/articles/10.1186/1477-7525-11-17