Paper recommender system Does anyone know a tool that gives paper recommendations based on a user defined list of papers? 

For example, if I've read papers A, B and C, I would like to find all papers related to A, B and C sorted by relevance. In this list a paper that cites all A, B and C or that is cited by all 3 should rank higher than a paper that is related to just one of them. 

EDIT: Some people suggested to use Google Scholar. The problem with Google Scholar is that it gives you papers related to just one article. If I have a base of 5 papers for my bibliography and I want to expand it, then I have to search for papers related to each of them individually and soon the number of options will become huge. I would prefer to have a smarter tool that analyze the links between the 5 papers and recommends articles related to all of them together. This would save a lot of time.
I'm not familiar with such a tool. But, if you reading an article on a scientific website such as http://www.sciencedirect.com/, a list of recommended or related papers will appear on the right hand side. Some of these recommended papers are very related, cited or been cited by the article you are reading. Google Scholar will list all papers that have cited a certain that too. I hope this helps.