I have seen a bunch of results concerning Matrix Completion, PCA, Compressed Sensing where a common theme has been to relax the Rank constraint/objective by replacing it with Nuclear Norm. I was wondering if there is a survey of some sort which collects these results, compares them and presents the basic underlying technique. I havent read the original papers yet so they might be the best reference but the purpose of the question is to know if there are other easier to understand references to get started on this topic with. Thanks in advance 
Reference for Nuclear Norm Relaxations
reference request;matrices