Statutes, CFRs, Executive Orders, Government Documents, etc. 

Founding Documents

Magna Charta
Declaration of Independence
Articles of Confederation
Constitution of the United States
Ordinance of 1787: Northwest Territory

 

Statutes, U.S. Code

26 USC § 7811  Taxpayer assistance orders
28 USC § 116
28 USC § 132
28 USC § 451
31 USC §§ 301-310
Rule 301, Federal Rules of Evidence
 

CFRs

Code of Federal Regulations - an excellent resource that gives several search options.
  27 CFR § 250.11
 
 

Executive Orders

Executive Order 10289
 
 

Court Cases

C. J. HENDRY CO. v. MOORE, 318 U.S. 133 (1943)
Tuccio v. USA Commissioner of Internal Revenue
 

Other

Michigan Legal Guidelines
An Index of Oklahoma Legislative Terms
Agreement on Tax Coordination Between Oklahoma Tax Commission and IRS Commissioner