Google scholar is a good resource for finding who has cited any given source. Search for a book or article in it and then look for the "Cited by" and a number beneath each of the search results. If you click that, you can often find very important information about that source, and develop your research. NOTE!!! Not everything you find on Google Scholar is from a peer-reviewed, reputable location. Be sure to do some research about the resources themselves. Use Google Scholar in conjunction with other resources.