Clements, J. (1987). Pennsylvania facts: A comprehensive look at Pennsylvania today county by county. Clements.
Citazione stile Chigago Style (17a edizione)Clements, John. Pennsylvania Facts: A Comprehensive Look at Pennsylvania Today County by County. Dallas, Tex: Clements, 1987.
Citatione MLA (9a ed.)Clements, John. Pennsylvania Facts: A Comprehensive Look at Pennsylvania Today County by County. Clements, 1987.
Attenzione: Queste citazioni potrebbero non essere precise al 100%.