Description and travel 17 History 17 Maps 17 Real property 17 Museums 16 Associations, institutions, etc 13 Directories 13 more ... Societies 13 Local transit 11 Societies, etc 10 Business enterprises 8 Economic conditions 7 Ethnic groups 7 Periodicals 6 Mafia 5 Railroads 5 Rents--Pennsylvania--Philadelphia Metropolitan Area 5 Transportation 5 Commerce 4 Regional planning 4 Social registers 4 Special libraries 4 Street-railroads 4 Vietnamese Americans 4 Central business districts 3 Commuting traffic 3 Ethnic relations 3 Guidebooks 3 Historic buildings 3 Korean Americans 3 Library cooperation 3 Roads 3 Archives 2 Asian Americans 2 Bicycle touring 2 Buildings 2 City traffic 2 College graduates 2 Debutantes 2 Finance, Public 2 less ...