The sources used for legal research are divided into two main categories—primary sources and secondary sources. Primary sources of law can include court decisions, statutes, and regulations. Secondary sources of law describe the law, discuss a legal problem, or offer analysis and commentary about a legal question. Secondary sources of law can include legal dictionaries, encyclopedias, law review articles and journals, treatises, and restatements. If you are unfamiliar with the legal topic or idea that you are researching, it is helpful to review secondary sources first for guidance.