In addition to primary administrative materials, secondary sources provide analysis and interpretation of administrative law principles. There are several sources that are commonly used references in the area of federal administrative law. Kenneth Culp Davis is one of the foremost administrative law scholars. His Administrative Law Treatise is perhaps the most scholarly current work in the area. The Treatise is now in its third edition and is co-authored by Professor Richard J. Pierce, Jr. Although the primary focus of the Treatise is federal law, a number of the topics are also relevant to state administrative law, such as, investigations, evidence, estoppel, and res judicata, to name a few. Another well-organized work whose focus is primarily federal law is Professor Charles H. Koch, Jr.’s Administrative Law and Practice. Schwartz’s Administrative Law  is a single volume treatment of administrative law and procedure. It includes discussion of both federal and state law. In addition, there are myriad law review articles that delve into specific areas of administrative law. Two prominent journals with useful articles are the Administrative Law Review published by the section of administrative law & regulatory practice of the American Bar Association through the Washington College of Law at American University and the Journal of the National Association of Administrative Law Judges published at the Loyola University Chicago School of Law.
Frank Cooper’s two-volume State Administrative Law is a comprehensive treatment of the state perspective. Although it has not been updated since 1965, it remains a useful resource since it is organized by topics common to state administrative law. A summary of Minnesota statutory and case law can be found in Dunnell Minnesota Digest. A concise introduction to the topic of Minnesota administrative procedure can be found in Keppel and Gilbert’s Minnesota Administrative Practice and Procedure. A more detailed treatment is found in the recently published Administrative Practice and Procedure authored by William J. Keppel and published as a part of Westlaw’s Minnesota Practice Series. Particularly helpful to readers of this treatise are Professor Keppel’s sections on data practices (§ 4.04), the open meeting law (§ 4.05) and the availability of and timing of judicial review (chapters 12 and 13). A variety of continuing education publications provide additional guidance on the Minnesota law, Bench and Bar, Hennepin Lawyer, and The Hamline Journal of Public Law are periodicals that provide coverage of the trends and changes in Minnesota administrative law. Bench and Bar’s Notes & Trends feature contains a column on case law and legislative developments in administrative law. An additional Minnesota administrative law publication is Administrative Law News, the newsletter of the administrative law section of the Minnesota State Bar Association. It summarizes recent Minnesota administrative case law.
The sole treatise dealing with state agency rulemaking is State Administrative Rule Making by Professor Arthur E. Bonfield. The treatise is organized along the lines of the 1981 Model State Administrative Procedure Act of which Professor Bonfield was the draftsman. However, the author has collected a wealth of state administrative law dealing with rulemaking, both in the original volume as well as the supplements.
 1-3 Kenneth C. Davis & Richard J. Pierce, Jr., Administrative Law Treatise (5th ed. 2010).
 Charles H. Koch, Administrative Law and Practice (3d ed. 2010).
 Bernard Schwartz, Administrative Law (8th ed. 2014).
 1 & 2 Frank E. Cooper, State Administrative Law (1965); see also Cheryl Rae. Nyberg, State Administrative Law Bibliography: Print and Electronic Media Sources (2000).
 1 Dunnell Minn. Digest, Administrative Law §§ 1.00-2.13 (6th ed. 2014).
 William Keppel & Dayton Gilbert, Minnesota Administrative Practice and Procedure (Advanced Legal Education 1982).
 William J. Keppel, Minnesota Practice Series: Administrative Practice and Procedure (2d ed., 2007).
 Arthur Bonfield, State Administrative Rule Making (1986).