American Dental Association v. Delta Dental Plans Association
You can buy your own copy of the ADA's Code on Dental Procedures and Nomenclature. The ADA, however, is not the only organization that publishes classification systems. The U.S. Government has an agency, the National Institute of Standards of Technology, that develops standards for science and commerce. Among other things, NIST regulates weights and measurements and keeps the official time of the United States through the use of atomic clocks.
Internationally, the International Organization for Standardization develops standards for almost everything. There are standards for champagne corks, transporting satellites and tennis rackets. There are even standards for developing standards.