Case Law:
Law Reviews:
These are not government sources- however, it is useful to highlight these as a possible source for a great depth of information that may look more narrowly at specific aspects of government policy.
Where to find:
The best results were found searching under Law Reviews: Search by Content Type for Law Reviews then in the search box choose atleast3(Puerto Rico). You will want to resort the results by relevance.
Congress issues reports, passes bills and often holds hearings, often with expert witnesses. Two documents were posted under the books tab. Here are the main committees, but note that other committees may bring up information on Puerto Rico as well.
Become familiar with the committees from both chambers of Congress:
Use the government search engine 
to find documents and sites posted by the government.