| A - General Works | 107 | 0.01 |
| AC - Collections. Series. | 1,085 | 0.08 |
| AE - Encyclopedias | 187 | 0.01 |
| AG - Dictionaries and other reference | 104 | 0.01 |
| AI - Indexes | 42 | 0.00 |
| AM - Museums. Collectors and collecting | 136 | 0.01 |
| AN - Newspapers | 14 | 0.00 |
| AP - Periodicals | 1,018 | 0.08 |
| AS - Academies and learned societies | 1,645 | 0.12 |
| AY - Yearbooks. Almanacs. Directories | 207 | 0.02 |
| AZ - History of scholarship and learning | 32 | 0.00 |
| B - Philosophy; Psychology; Religion | 4,446 | 0.33 |
| BC - Logic | 317 | 0.02 |
| BD - Speculative philosophy | 758 | 0.06 |
| BF - Psychology | 3,056 | 0.23 |
| BH - Aesthetics | 163 | 0.01 |
| BJ - Ethics | 1,033 | 0.08 |
| BL - Religions. Mythology. Rationalism | 2,073 | 0.15 |
| BM - Judaism | 449 | 0.03 |
| BP - Islam. Bahaism. Theosophy | 549 | 0.04 |
| BQ - Buddhism | 246 | 0.02 |
| BR - Christianity | 2,234 | 0.17 |
| BS - The Bible | 2,992 | 0.22 |
| BT - Doctrinal Theology | 1,705 | 0.13 |
| BV - Practical Theology | 2,463 | 0.18 |
| BX - Christian Denominations | 6,255 | 0.46 |
| C - Auxiliary Science of History | 16,492 | 1.22 |
| CB - History of Civilization | 383 | 0.03 |
| CC - Archaeology | 80 | 0.01 |
| CD - Diplomatics. Archives. Seals | 775 | 0.06 |
| CE - Technical Chronology. Calendar | 88 | 0.01 |
| CJ - Numismatics | 483 | 0.04 |
| CN - Inscriptions. Epigraphy | 29 | 0.00 |
| CR - Heraldry | 250 | 0.02 |
| CS - Genealogy | 752 | 0.06 |
| CT - Biography | 651 | 0.05 |
| D - History General | 6,775 | 0.50 |
| DA - History of Great Britain - History of Ireland - History of the British Isles | 6,753 | 0.50 |
| DB - History of Austria - Liechtenstein - Hungary - Czechoslovakia | 1,495 | 0.11 |
| DC - History of France - Andorra - Monaco | 6,601 | 0.49 |
| DD - History of Germany | 2,228 | 0.17 |
| DE - History of the Greco-Roman World | 244 | 0.02 |
| DF - History of Greece | 889 | 0.07 |
| DG - History of Italy - Malta | 2,442 | 0.18 |
| DH - History of Low Countries - Benelux Countries | 482 | 0.04 |
| DJ - History of the Netherlands | 350 | 0.03 |
| DJK - History of Eastern Europe | 8 | 0.00 |
| DK - History of Russia; Soviet Union; Former Soviet Republics - History of Poland | 2,262 | 0.17 |
| DL - History of Northern Europe; Scandavia | 416 | 0.03 |
| DP - History of Spain - Portugal | 1,101 | 0.08 |
| DQ - History of Switzerland | 231 | 0.02 |
| DR - History of the Balkan Peninsula | 1,049 | 0.08 |
| DS - History of Asia | 7,704 | 0.57 |
| DT - History of Africa | 2,058 | 0.15 |
| DU - History of Oceania (South Seas) | 584 | 0.04 |
| DX - History of Gypsies | 43 | 0.00 |
| E - History of America | 11,950 | 0.89 |
| F - Local History of the United States and British; French; and Latin America | 11,229 | 0.83 |
| G - Geography; Anthropology; Recreation | 2,031 | 0.15 |
| GA - Mathematical geography; Cartography | 222 | 0.02 |
| GB - Physical geography | 3,827 | 0.28 |
| GC - Oceanography | 175 | 0.01 |
| GE - Environmental Sciences | 12 | 0.00 |
| GF - Human ecology; Anthropogeography | 62 | 0.00 |
| GN - Anthropology | 1,257 | 0.09 |
| GR - Folklore | 924 | 0.07 |
| GT - Manners and customs (General) | 194 | 0.01 |
| GV - Recreation; Leisure | 920 | 0.07 |
| H - Social sciences (General) | 2,116 | 0.16 |
| HA - Statistics | 895 | 0.07 |
| HB - Economic theory; Demography | 1,747 | 0.13 |
| HC - Economic history and conditions | 2,793 | 0.21 |
| HD - Industries; Land use; Labor | 10,109 | 0.75 |
| HE - Transportation and communications | 4,423 | 0.33 |
| HF - Commerce | 3,599 | 0.27 |
| HG - Finance | 2,881 | 0.21 |
| HJ - Public Finance | 2,461 | 0.18 |
| HM - Sociology (General) | 667 | 0.05 |
| HN - Social history and conditions; Social problems; Social reform | 713 | 0.05 |
| HQ - The family; Marriage; Woman; Sexuality | 1,332 | 0.10 |
| HS - Societies: secret; benevolent; etc. | 362 | 0.03 |
| HT - Communities; Classes; Races | 495 | 0.04 |
| HV - Social pathology; Social and public welfare ; Criminology | 4,854 | 0.36 |
| HX - Socialism. Communism. Anarchism | 1,394 | 0.10 |
| J - General legislative and executive papers | 1,020 | 0.08 |
| JA - Political science (General) | 572 | 0.04 |
| JC - Political theory. The state. Theories of the state. | 972 | 0.07 |
| JF - Political institutions and public administration - General | 363 | 0.03 |
| JJ - Political institutions and public administration - North America | 1 | 0.00 |
| JK - Political institutions and public administration - United States | 2,761 | 0.20 |
| JL - Political institutions and public administration - Canada; Latin America; etc. | 136 | 0.01 |
| JN - Political institutions and public administration - Europe | 1,455 | 0.11 |
| JQ - Political Institutions and public administration - Asia; Africa; Australia; Pacific Area; etc. | 326 | 0.02 |
| JS - Local government. Municipal government | 1,169 | 0.09 |
| JV - Colonies and colonization. Emigration and Immigration. International migration | 437 | 0.03 |
| JX - International law (obsolete) | 2,272 | 0.17 |
| JZ - International relations | 61 | 0.00 |
| K - Law | 133 | 0.01 |
| KDK - Law (United Kingdom and Ireland | 39 | 0.00 |
| KDZ - Law (America. North America) | 5 | 0.00 |
| KE - Law (Canada) | 3 | 0.00 |
| KF - Law (United States) | 3,262 | 0.24 |
| KJ - Law (Europe) | 22 | 0.00 |
| KK - Law (Europe) | 23 | 0.00 |
| KL - Law (History of law. The ancient orient) | 7 | 0.00 |
| KM - Law (Asia) | 3 | 0.00 |
| KN - Law (South Asia. Southeast Asia. East Asia) | 8 | 0.00 |
| KP - Law (South Asia. Southeast Asia. East Asia) | 1 | 0.00 |
| KR - Law (Africa) | 1 | 0.00 |
| KS - Law (Africa) | 46 | 0.00 |
| KT - Law (Africa) | 1 | 0.00 |
| KZ - Law of Nations. International law | 5 | 0.00 |
| L - Education | 1,004 | 0.07 |
| LA - History of Education | 1,460 | 0.11 |
| LB - Theory and practice of education | 5,115 | 0.38 |
| LC - Special aspects of education | 1,686 | 0.12 |
| LD - Education (Individual Institutions - United States) | 1,726 | 0.13 |
| LE - Education (Individual Institutions - America (except United States)) | 62 | 0.00 |
| LF - Education (Individual Institutions - Europe) | 693 | 0.05 |
| LG - Education (Individual Institutions - Asia; Africa; Indian Ocean Islands; Australia; New Zealand; Pacific Islands) | 78 | 0.01 |
| LH - College and school magazines and papers | 91 | 0.01 |
| LJ - Student fraternities; United States | 131 | 0.01 |
| LT - Textbooks | 1 | 0.00 |
| M - Printed Music | 3,611 | 0.27 |
| ML - Literature on music | 2,565 | 0.19 |
| MT - Musical instruction and study | 745 | 0.06 |
| N - Visual arts | 2,825 | 0.21 |
| NA - Architecture | 2,165 | 0.16 |
| NB - Sculpture | 400 | 0.03 |
| NC - Drawing. Design. Illustration | 332 | 0.02 |
| ND - Painting | 1,599 | 0.12 |
| NE - Print media | 358 | 0.03 |
| NK - Decorative arts | 917 | 0.07 |
| NX - Arts in general | 66 | 0.00 |
| P - Language and Literature | 158 | 0.01 |
| PA - Greek and Latin language and literature | 1,068 | 0.08 |
| PB - Modern languages; Celtic languages | 65 | 0.00 |
| PC - Romanic languages | 248 | 0.02 |
| PE - English language | 229 | 0.02 |
| PF - West Germanic languages | 62 | 0.00 |
| PG - Slavic languages; Baltic languages; Albanian language | 489 | 0.04 |
| PH - Uralic languages; Basque language | 92 | 0.01 |
| PJ - Oriental philology and literature | 1,141 | 0.08 |
| PK - Indo-Iranian philology and literature | 529 | 0.04 |
| PL - Languages of Eastern Asia; Africa; Oceania | 2,803 | 0.21 |
| PM - Hyperborean; Indian; and artificial languages | 84 | 0.01 |
| PN - Literature (General) | 1,529 | 0.11 |
| PQ - French literature - Italian literature - Spanish literature - Portuguese literature | 2,037 | 0.15 |
| PR - English literature | 6,744 | 0.50 |
| PS - American literature | 2,084 | 0.15 |
| PT - German; Dutch; Scandinavian; Old Norse; Old Icelandic; Old Norwegian; Modern Icelandic; Faroese; Danish; Norwegian; and Swedish literature; Flemish literature since 1830 | 1,154 | 0.09 |
| PZ - Fiction and juvenile belles lettres | 311 | 0.02 |
| Q - Science (General) | 1,980 | 0.15 |
| QA - Mathematics | 6,917 | 0.51 |
| QB - Astronomy | 2,220 | 0.16 |
| QC - Physics | 4,396 | 0.33 |
| QD - Chemistry | 2,823 | 0.21 |
| QE - Geology | 3,210 | 0.24 |
| QH - Natural history - Biology | 2,870 | 0.21 |
| QK - Botany | 3,582 | 0.27 |
| QL - Zoology | 3,564 | 0.26 |
| QM - Human anatomy | 273 | 0.02 |
| QP - Physiology | 668 | 0.05 |
| QR - Microbiology | 200 | 0.01 |
| R - Medicine (General) | 567 | 0.04 |
| RA - Public aspects of medicine | 2,161 | 0.16 |
| RB - Pathology | 145 | 0.01 |
| RC - Internal medicine | 1,395 | 0.10 |
| RD - Surgery | 406 | 0.03 |
| RE - Ophthalmology | 60 | 0.00 |
| RF - Otorhinolaryngology | 33 | 0.00 |
| RG - Gynecology and obstetrics | 127 | 0.01 |
| RJ - Pediatrics | 220 | 0.02 |
| RK - Dentistry | 935 | 0.07 |
| RL - Dermatology | 23 | 0.00 |
| RM - Therapeutics. Pharmacology | 282 | 0.02 |
| RS - Pharmacy and materia medica | 566 | 0.04 |
| RT - Nursing | 291 | 0.02 |
| RV - Botanic; Thomsonian; and eclectic medicine | 6 | 0.00 |
| RX - Homeopathy | 10 | 0.00 |
| RZ - Other systems of medicine | 10 | 0.00 |
| S - Agriculture (General) | 1,713 | 0.13 |
| SB - Plant culture | 1,821 | 0.13 |
| SD - Forestry | 3,622 | 0.27 |
| SF - Animal culture | 568 | 0.04 |
| SH - Aquaculture. Fisheries. Angling. | 487 | 0.04 |
| SK - Hunting sports | 339 | 0.03 |
| T - Technology (General) | 1,222 | 0.09 |
| TA - Engineering (General). Civil Engineering | 1,752 | 0.13 |
| TC - Hydraulic engineering - Ocean Engineering | 1,454 | 0.11 |
| TD - Environmental technology. Sanitary engineering | 2,196 | 0.16 |
| TE - Highway engineering. Roads and pavements | 585 | 0.04 |
| TF - Railroad engineering and operation | 1,030 | 0.08 |
| TG - Bridge engineering | 478 | 0.04 |
| TH - Building construction | 601 | 0.04 |
| TJ - Mechanical engineering and machinery | 2,035 | 0.15 |
| TK - Electrical engineering. Electronics. Nuclear engineering | 2,862 | 0.21 |
| TL - Motor vehicles. Aeronautics. Astronautics | 2,021 | 0.15 |
| TN - Mining engineering. Metallurgy | 1,728 | 0.13 |
| TP - Chemical technology | 1,381 | 0.10 |
| TR - Photography | 382 | 0.03 |
| TS - Manufactures | 774 | 0.06 |
| TT - Handicrafts. Arts and crafts | 119 | 0.01 |
| TX - Home economics | 505 | 0.04 |
| U - Military Science (General) | 923 | 0.07 |
| UA - Armies: Organization; distribution; military situation | 1,052 | 0.08 |
| UB - Military administration | 672 | 0.05 |
| UC - Maintenance and transportation | 195 | 0.01 |
| UD - Infantry | 78 | 0.01 |
| UE - Cavalry. Armor | 47 | 0.00 |
| UF - Artillery | 293 | 0.02 |
| UG - Military engineering | 583 | 0.04 |
| UH - Other services | 142 | 0.01 |
| V - Naval science (General) | 263 | 0.02 |
| VA - Navies: Organization; distribution; naval situation | 154 | 0.01 |
| VB - Naval administration | 53 | 0.00 |
| VC - Naval maintenance | 41 | 0.00 |
| VD - Naval seaman | 2 | 0.00 |
| VE - Marines | 39 | 0.00 |
| VF - Naval ordnance | 27 | 0.00 |
| VG - Minor services of navies | 81 | 0.01 |
| VK - Navigation. Merchant marine | 517 | 0.04 |
| VM - Naval architecture. Shipbuilding. Marine engineering | 588 | 0.04 |
| Z - Books (General). Writing. Paleography. Book industries and trade. Libraries. Bibliography | 12,435 | 0.92 |
| ZA - Information Resources | 5 | 0.00 |
Digital Library