Specifically, it really doesn't matter how many pages and how many references you are including in your paper. But the important thing is, you should include all the important and latest original papers from excellent publishing houses (IEEE, Elsevier, Springer, Willey etc.) Mostly SCI Journals. Don't go and include cheap journal papers and unnecessarily increase your Reference section. Also include specific section for discussion of the problems associated with previous and present approaches. Also, add tables considering parameters and advantage s and disadvantages of the previous approaches in your paper. So that later on if someone refer your paper, he/she get quality information from the paper.