Treatises are scholarly works written in an area of law by legal scholars. The authors are legal experts, usually professors or practitioners, who treat the topic in depth, in a sngle volume or a multi-volume set, in looseleaf format or online. Treatises are considered secondary authority and they are an excellent starting point when one needs to learn about an area of law. Treatises include tables of conents, tables of cases, tables of statutes, indexes, appendices and are continuously updated, either by pocket part or by replacement pages if in looseleaf format.
A number of legal research books discuss the importance of treatises as a valuable category of secondary authority. See the following:
Barkan, Steven M., et al., Fundamentals of Legal Research, 10th ed. (2015)
Gallacher, Ian, Legal Communication and Research (2015)
Kunz, Christina, The Process of Legal Research: Authorities and Options, 8th ed. (2012)
Sloan, Amy E., Basic Legal Research: Tools and Strategies, 5th ed. (2012)
Svengalis, Kendall F., Legal Information Buyer's Guide & Reference Manual, (2015) Chapter 27 extensively covers "Legal Treatises & Other Specialty Material" in sixty-five subject areas.
See also the article in Student Lawyer, Treatises: Let the Experts Serve You" by Mark Cooney entitled Volume 43, number 2, October 2014, page 16.
See also the article in Law Library Journal, "Possible Futures for the Legal Treatise in an Environment of Wikis, Blogs, and Myriad Online Primary Law Sources" by Peter W. Martin, Volume 108, number 1, Winter 2016, page 7.