Dates in: Checklist of United States trees (native and naturalized). U.S. Dep. Agric., Agric. Handb. 541: 340. 1979, https://books.google.ch/books?id=b5pywYdd_tAC&pg=PA340&dq=Francis+Irving+Righter+(1897%E2%80%931972)&hl=de&sa=X&ved=2ahUKEwj6pMSX3v77AhW57rsIHVAPCh4Q6AF6BAgEEAI#v=onepage&q=Francis%20Irving%20Righter%20(1897%E2%80%931972)&f=false (via Boris Heuer)