Use key words to search for at least one relevant article in an index. Then find the index terms, sometimes called subjects, used to tag the article. Click on any relevant index terms to find all articles indexed with the same term. This lets you have more confidence that you have found every text that deals with the relevant concept in that index that could preempt your paper. With multiple keyword searches you never know if you have found every relevant text, but with an index someone has read each article and tagged it with index terms if it deals with the relevant concept.
Articles may be available here before they get included in the indexes above, and working papers that may never get published are also available here. Search the most recent texts with SSRN--but you are limited to keyword searching because the index terms that they use are not consistent across all content like in the formal indexes above.
Although these platforms don't index legal periodicals you can use keywords to search law reviews and discover any other relevant text.
While in the "Develop a Topic" page above you ideally already searched for information relevant to you paper on these research platforms, this is here in case you haven't yet done a search for just the articles in legal periodicals that could preempt your paper now that it is developed.