The asterisk * is a wildcard so feminis* finds feminist, feminism theor* finds theory, theories, theoretical
Login to Quick Search for full access. Search with your theorist's name (try just using the last name) or the name of the theory and a few key terms for your topic. You may find sources by your theorist or that cite your theorist. There are other ways to try and do this, so don't get too bogged down if the strategy doesn't work for you.