SECONDARY SOURCES OF LAW IN NIGERIA.
Secondary sources of law include encyclopedia,law reviews,treaties,restatements,law journals, and secondary sources are a good way to start research and often have citations to primary sources. Secondary sources are a good way to begin any law research because secondary sources explains legal principles more thoroughly than a single case or statute,although the primary sources of law which includes case law,statutes and regulations establish the law on a given topic.
 Secondary sources of law are particularly useful for learning the basic of a particular area of law,understanding key terms of art in an area,identifying essential cases and statutes.
LEGAL ENCYCLOPEDIAS 
Legal encyclopedias contain brief,broad summaries of legal topics,providing introductions to legal topics and explaining relevant terms of art and they also provide citation to primary sources of law. A country can have their own legal encyclopedias based on their constitution.
LAW JOURNALS 
 Law Journal or reviews are another secondary source for legal research,law reviews are scholarly publications edited by law students and they contain both lengthy articles and shorter essays by professors and lawyers,law reviews focus on emerging areas of law and they can offer more critical commentary than a law journal.
RESTATEMENTS
Restatements are highly disregarded distillation of common law,restatements are necessary when it is determined that a previous statement contained a material inaccuracy. Many restatements are the result of innocent mistakes and basic interpretations however some can raise red flags.
However also anything more than the actual law is secondary source of law.
In Nigeria, law reports such as The Nigerian weekly law reports and All Nigerian law reports are law reports.