Before you start doing in-depth research on a legal policy topic, you may wish to consult some general works that will provide an overview or a "lay of the land" on your topic. Good background sources include:
Encyclopedia of Social Work: available online and in print: DEWEY REF HV 12 E53 2008
Comprehensive Handbook of Social Work and Social Welfare: volume 4 is about social policy: DEWEY REF HV 40 C635 2008
CQ Researcher Plus: provides "plain english" overviews of important Federal legislation. Online and in print: DEWEY REF JK 1 C66
LawCrawler Search engine of legal resources worldwide.
Legal Information Institute Site maintained at Cornell Law School. Well designed access to American constitutions, codes, court opinions, and 'Spotlight' on hot topics.