Gross, Doug. Eagle-Watching in Lower Susquehanna River, Lancaster and York counties. Pennsylvania Game Commission. 2011-08-09 [2021-04-10]. (原始内容存档于2020-09-25)
Charles; Hansen, Amelia. Wildlife of Pennsylvania and the Northeast. Stackpole Books. 2000. ISBN 9780811728997 (英语). Lancaster, Frank Maurice. The inheritance