The system divides all knowledge into twenty-one basic classes, each identified by a single letter of the alphabet. Most of these alphabetical classes are further divided into more specific subclasses, identified by two-letter, or occasionally three-letter, combinations
ALA-LC Romanization Tables
The libraries follow the romanization standards used in the Library of Congress
The Library of Congress transliteration tables for Slavic and non-Slavic languages of the region that use Cyrillic alphabets. Here are found transliteration tables for Azerbaijani, Belarusian, Bulgarian, Kazakh, Macedonian, Serbian, Russian, Tajik, Tatar, Turkmen, Ukrainian and Uzbek languages