U.S. trademark regulations are found in parts 2, 6-7 of title 37 of the Code of Federal Regulations (C.F.R.). The library has a physical set of official C.F.R. (See the call number listed below to find these in the stacks.) Electronic versions are available through the Government Printing Office, Lexis and Westlaw. HeinOnline offers full historic coverage of the C.F.R.
Trademark Manual of Examining Procedure (TMEP)
Secondary Sources on TTAB Practice