| A - General Works | H - Business. Social Sciences | Q - Science |
| B - Philosophy. Psychology. Religion | J - Political Science | R - Medicine |
| C - Auxiliary Sciences of History | K - Law | S - Agriculture |
| D - History (General) | L - Education | T - Technology |
| E - History (United States) | M - Music | U - Military Science |
| F - History (The Americas, U.S. Local) | N - Fine Arts | V - Naval Science |
| G - Geography. Anthropology | P - Language and Literature | Z - Bibliography |