Pigg, K. B.; Ickert-Bond, S. M.; Wen, J. (2004). "Anatomically preserved Liquidambar (Altingiaceae) from the middle Miocene of Yakima Canyon, Washington state, USA, and its biogeographic implications". American Journal of Botany. 91 (3): 499–509. doi:10.3732/ajb.91.3.499. PMID21653405.
Pigg, K.B. (2001). "Anatomically preserved Woodwardia virginica (Blechnaceae) and a new Filicalean fern from the Middle Miocene Yakima Canyon Flora of central Washington, USA". American Journal of Botany. 88 (5): 777–787. doi:10.2307/2657030. JSTOR2657030. PMID11353703.
jstor.org
Pigg, K.B. (2001). "Anatomically preserved Woodwardia virginica (Blechnaceae) and a new Filicalean fern from the Middle Miocene Yakima Canyon Flora of central Washington, USA". American Journal of Botany. 88 (5): 777–787. doi:10.2307/2657030. JSTOR2657030. PMID11353703.
nih.gov
pubmed.ncbi.nlm.nih.gov
Pigg, K. B.; Ickert-Bond, S. M.; Wen, J. (2004). "Anatomically preserved Liquidambar (Altingiaceae) from the middle Miocene of Yakima Canyon, Washington state, USA, and its biogeographic implications". American Journal of Botany. 91 (3): 499–509. doi:10.3732/ajb.91.3.499. PMID21653405.
Pigg, K.B. (2001). "Anatomically preserved Woodwardia virginica (Blechnaceae) and a new Filicalean fern from the Middle Miocene Yakima Canyon Flora of central Washington, USA". American Journal of Botany. 88 (5): 777–787. doi:10.2307/2657030. JSTOR2657030. PMID11353703.