What subjects do the call letters cover?
Subclass H Social sciences (General).
Subclass HA Statistics.
Subclass HB Economic theory. Demography.
Subclass HC Economic history and conditions.
Subclass HD Industries. Land use. Labor.
Subclass HE Transportation and communications.
Subclass HF Commerce.
Subclass HG Finance.
Subclass HJ Public finance.
Subclass HM Sociology.
Subclass HN Social history and conditions. Social problems.
Subclass HQ The Family. Marriage. Women.
Subclass HS Societies: secret, benevolent, etc.
Subclass HT Communities. Classes. Races.
Subclass HV Social pathology. Social and public welfare.
Subclass HX Socialism. Communism. Anarchism.