The elements of a citation are:
Source abbreviation (Tex. Admin. Code for the Texas Administrative Code)
For example, for the citation 31 Tex. Admin. Code § 201.1 (2005):
"31" is the Title number of the Texas Administrative Code.
"Tex. Admin. Code" is the abbreviation for the Texas Administrative Code.
"§ 201.1" is the section of Title 31 in which the text of the relevant regulation can be found.
"2005" indicates the year of publication of the volume of the Texas Administrative Code in which the regulation was found.
The General Index is a subject index arranged in alphabetical order, located in the last two volumes. Under general subject headings and specific sub-headings, the General Index provides detailed cross-references to relevant rules and regulations adopted by the various agencies, commissions, and departments of the State of Texas and codified in the TAC.
Each volume of the unofficial version of the TAC, published by Thomson West, is replaced annually. For the most current information, look at the Texas Register (weekly publication of proposed, passed, and amended agency regulations).