SOURCES FOR RAW DATA

Bills--All proposed legislation, and nearly all formal actions by either of the two houses, take the form of a bill or resolution.
A bill is a legislative proposal of a general nature.
A bill may propose either a public or private matter.
The form of a law before it is passed by Congress and signed by the President.
Identified by H.R. or S. -- House or Senate resolution.
H.R. 1 -- The house resolution number for Clean Air Act of 1966
**Note**There are other acronuoms, but these are the two most used.
http://thomas.loc.gov/home/enactment/enactlaw.pdf

Laws--Legislation that has been approved by Congress and signed by the President.
Once a bill becomes a law it is assigned a public law number, P.L. 89-272
107=Number of the Congress, 89th Congress, 1965-1966
Once a law is give a public law number it is codified into the compilation of current U.S. laws known as the United States Code.
42 U.S.C 7521=The U.S. Code section where you will find the current text of the Clean Air Act.

Regulations--A rule or order, having a legal force, issued by an administrative agency or a local government.
Black's Law Dictionary
Sometimes a law has rules, regulations, attached to its enforcement. These are found in the Code of Federal Regulations.
23 CFR 633.21=Regulation relating to highways and the administration of the Clean Air Act.