In addition to published papers in law- and non-law journals, you should also research economic "working papers." Working papers may still be present in these databases years after they are published in final form, so you should search other journal databases to be sure that you are citing to the final, published article. However, working papers are largely complete, and are made available for scholars' comments. Often times, working papers can have substantial influence on policy.
Databases containing economics working papers: