1. Park DH, Kim HK, Choi IY, Kim JK (2012) A literature review and classification of recommender systems research. Expert Syst Appl 39:10059–10072. doi: 10.1016/j.eswa.2012.02.038
2. Vozalis MG, Margaritis KG (2007) Using SVD and demographic data for the enhancement of generalized collaborative filtering. Inf Sci 177:3017–3037. doi: 10.1016/j.ins.2007.02.036
3. Anand D, Bharadwaj KK (2011) Utilizing various sparsity measures for enhancing accuracy of collaborative recommender systems based on local and global similarities. Expert Syst Appl 38:5101–5109. doi: 10.1016/j.eswa.2010.09.141
4. Chen Y, Wu C, Xie M, Guo X (2011) Solving the sparsity problem in recommender systems using association retrieval. J Comput 6:1896–1902
5. Zhang J, Lin Y, Lin M, Liu J (2016) An effective collaborative filtering algorithm based on user preference clustering. Appl Intell:1–11