300s: Social Sciences
* 300-309: Sociology
* 300: Sociology in general
* 301: Social structure
* 302: Social psychology
* 303: Demography
* 304: Social problems and social movements
* 305: Ethnology, cultural anthropology
* 306: Social change
* 307: Community organization
* 308: Applied sociology
* 309: Regional sociology, urban sociology
* 310-319: Statistics
* 310: Statistics in general
* 311: Statistical methods
* 312: Demography
* 313: Vital statistics
* 314: Social statistics
* 315: International statistics
* 316: Statistical services
* 317: Statistical tables, charts
* 318: Statistical techniques
* 319: Statistical computing
* 320-329: Political Science
* 320: Political science in general
* 321: Political theory
* 322: Political parties
* 323: Civil rights and liberties
* 324: Elections and voting
* 325: Immigration and emigration
* 326: International law
* 327: International relations
* 328: Legislative bodies
* 329: Political movements and organizations
* 330-339: Economics
* 330: Economics in general
* 331: Labor economics
* 332: Financial economics
* 333: Land economics
* 334: Co-operation
* 335: Socialism and communism
* 336: Public finance
* 337: International trade
* 338: Production and distribution
* 339: Economic conditions and policies
* 340-349: Law
* 340: Law in general
* 341: International law
* 342: Constitutional law
* 343: Administrative law
* 344: Criminal law
* 345: Civil procedure
* 346: Commercial law
* 347: Property law
* 348: Family law
* 349: Legal history
* 350-359: Public Administration
* 350: Public administration in general
* 351: Central government
* 352: Local government
* 353: Military administration
* 354: Comparative public administration
* 355: Military science
* 356: Naval science
* 357: Police science
* 358: Aeronautics
* 359: Naval administration
* 360-369: Social Welfare
* 360: Social welfare in general
* 361: Social work
* 362: Social pathology
* 363: Public health
* 364: Criminology
* 365: Prisons and penology
* 366: Social services
* 367: Social clubs
* 368: Insurance
* 369: Voluntary organizations
* 370-379: Education
* 370: Education in general
* 371: Teaching methods
* 372: Elementary education
* 373: Secondary education
* 374: Adult education
* 375: Curriculum
* 376: Special education
* 377: Religious education
* 378: Higher education
* 379: Public education
* 380-389: Commerce, Communication, Transportation
* 380: Commerce in general
* 381: Domestic trade
* 382: Foreign trade
* 383: Postal service
* 384: Telecommunications
* 385: Transportation in general
* 386: Water transportation
* 387: Air transportation
* 388: Road transportation
* 389: Transportation law and regulation
* 390-399: Customs, Folklore, Recreation
* 390: Customs and folklore in general
* 391: Costume and fashion
* 392: Manners and etiquette
* 393: Rituals and ceremonies
* 394: Recreation and sports
* 395: Holidays and festivals
* 396: Women's studies
* 397: Men's studies
* 398: Folklore
* 399: Popular culture
This is just a brief overview. Each subcategory has many more specific topics within it.
It's important to remember that this is a classification system, not a rigid definition. Overlapping and cross-disciplinary topics exist.