Flowering Plants of Pennsylvania and New Jersey
URL: http://worldplants.webarchiv.kit.edu/PA/index.php
A Pictorial Database – Version 3.26. With 9945 photos of 3051 taxa (total 3569 taxa). By Michael Hassler, Bruchsal, Germany – Technical realization by Bernd Schmitt. In cooperation with Botanical Garden of the Karlsruhe Institute of Technology.