Subject
Historic sites Law and legislation
14
Wild and scenic rivers Law and legislation
11
Groundwater
9
Groundwater Pollution
8
Land titles Registration and transfer
8
Water quality
8
Geophysical well logging
7
Adult education
6
Gettysburg National Military Park (Pa.) Boundaries
6
Historic sites
6
Water table
6
White Clay Creek (Pa. and Del.)
6
Courthouses
5
Cultural property Protection Law and legislation
5
Longwall mining
5
Water resources development
5
Aquifers
4
Coal Geology
4
Groundwater Quality
4
Juvenile delinquency Prevention
4
Lackawanna Valley National Heritage Area (Pa.)
4
Military parks Law and legislation
4
Minority older people Services for
4
Public buildings
4
Radon Environmental aspects
4
Steamtown National Historic Site (Scranton, Pa.)
4
Abandoned coal mines Fires and fire prevention
3
Acculturation
3
Allegheny River (Pa. and N.Y.)
3
Barter
3
Borings
3
Geology
3
Gettysburg National Military Park (Pa.)
3
Ground control (Mining)
3
Hydroelectric power plants Law and legislation
3
Hydroelectric power plants Licenses
3
Independence Mall (Philadelphia, Pa.)
3
Independence National Historical Park (Philadelphia, Pa.)
3
Management
3
National parks and reserves
3
Older people Services for
3
Older volunteers in social service
3
River channels
3
Rules and practice
3
Veterans Medical care
3
Visitors' centers Law and legislation
3
Water Composition
3
Water-supply
3
Wetlands
3
Acid mine drainage
2
more ...