Importing to the United States?  It is essential to reference the Harmonized Tariff Schedule of the U.S (HTSUS) or sometimes referred to as Harmonized Tariff Schedule of the United States Annotated (HTSA).  This publication contains import tariff schedule and classification numbers used in determining classification and rate of duty, quota, restrictions, and special programs.  It is especially relevant for importing to the USA but also may be used for exporting from the USA to other foreign nations.