A  – General Works

AE – Encyclopedias

AI  – Indexes

AN – Newspapers

AP – Periodicals

B – Philosophy, Psychology

B-BD – Philosophy

BF – Psychology

BH – Exsthetics

BJ – Ethics

BL-BX – Religions, Mythology

C – History (Auxiliary sciences: archaeology, genealogy, etc.)

D – History (Except America)

DA – Great Britain

DC – France

DD – Germany

DK – Russia

DS - Asia

E-F – America and U.S.

F1-F970 – United States

F1201-F3899 – Latin America

G – Geography, Anthropology

G-GF – Geography, Travel, Atlases

GN – Anthropology, Ethnography

GR – Folklore

GV – Sports

H – Social Sciences

HA-HJ – Economics

HM-HQ – Sociology

HX - Communism, Socialism, Anarchism

J – Political Science

K – Law

L – Education

M – Music

N – Fine Arts

NA – Architecture

NB – Sculpture & Related Arts

NC – Graphic Arts

ND – Painting

NK – Applied Arts

NX – The arts in general

P – Language and Literature

PA – Classical Philology

PB-PH – Modern European Languages

PJ-PL – Oriental Languages

PQ – Romance Literature

PR – English Literature

PS – American Literature

PT – German Literature

Q – Science

QA – Mathematics

QB – Astronomy

QC – Physics

QD – Chemistry

QE – Geology

QH – Natural History

QK – Botany

QL – Zoology

QM – Human anatomy

QP – Physiology

QR – Bacteriology

R – Medicine

S – Agriculture

T – Technology & Engineering

U – Military Science

V – Naval Science

Z – Bibliography & Library Science