Pigg, K.B.; Manchester, S.R.; Wehr, W.C. (2003). "Corylus, Carpinus, and Palaeocarpinus (Betulaceae) from the Middle Eocene Klondike Mountain and Allenby Formations of Northwestern North America". International Journal of Plant Sciences. 164 (5): 807–822. doi:10.1086/376816. S2CID19802370.
Forest, F.; Savolainen, V.; Chase, M. W.; Lupia, R.; Bruneau, A.; Crane, P. R. (2005). "Teasing apart molecular- versus fossil-based error estimates when dating phylogenetic trees: a case study in the birch family (Betulaceae)". Systematic Botany. 30 (1): 118–133. doi:10.1600/0363644053661850. S2CID86080433.
Pigg, K.B.; Manchester, S.R.; Wehr, W.C. (2003). "Corylus, Carpinus, and Palaeocarpinus (Betulaceae) from the Middle Eocene Klondike Mountain and Allenby Formations of Northwestern North America". International Journal of Plant Sciences. 164 (5): 807–822. doi:10.1086/376816. S2CID19802370.
Forest, F.; Savolainen, V.; Chase, M. W.; Lupia, R.; Bruneau, A.; Crane, P. R. (2005). "Teasing apart molecular- versus fossil-based error estimates when dating phylogenetic trees: a case study in the birch family (Betulaceae)". Systematic Botany. 30 (1): 118–133. doi:10.1600/0363644053661850. S2CID86080433.