According to the Merriam Webster Dictionary, an op-ed is "An essay in a newspaper or magazine that gives the opinion of the writer and that is written by someone who is not employed by the newspaper or magazine" and stands for opposite editorial. Op-Eds are sometimes referred to as Opinions and/or Commentary.
Search for journal articles on most topics. This multi-disciplinary database is a good place to start if you don't know where else to begin. (EBSCO)
Search for articles from legal journals, law reviews, yearbooks, and other publications from bar associations, universities, and governments. This database also includes citations of thousands of books. It is international in scope, also including information from Canada, Great Britain, Ireland, New Zealand, and Australia. (EBSCO)
Search for articles from journals that publish feminist research in areas of sociology, history, political science, public policy, international relations, arts and humanities, business, and education. (EBSCO)