Unknown. (2023). Pennsylvania department of forestry. Forest Research Institute.
Chicago-čujuhus (17. p.)Unknown. Pennsylvania Department of Forestry. Forest Research Institute, 2023.
MLA-čujuhus (9. p.)Unknown. Pennsylvania Department of Forestry. Forest Research Institute, 2023.
Muitte dárkkistit čujuhemiid riektatvuođa, ovdal go geavahat daid iežat deavsttas.