Information on the web
Sinkholes in PA
Florida sinkholes
Florida sinkholes are not totally similar to sinkholes in Pennsylvania but the mechanisms of formation are generally the same.
Other Info
The Karst Pages - Info on dye tracing and general karst aquifer info from Western Kentucky Univ.
References
Foose, Richard M. (1953) "Ground-water Behavior in the Hershey Valley, Pennsylvania", Geological Society of America Bulletin, v. 64, p. 623-645.
Newton, J.G. (1987) Development of Sinkholes Resulting From Man's Activities in the Eastern United States. US Geological Survey, Circular 968.
White, William B. (1988) Geomorphology and Hydrology of Karst Terrains. Oxford University Press.