1. A Geologic Time Scale 1982
2. BOND, W.J., BOTANICAL JOURNAL OF THE LINNEAN SOCIETY 36: 227 (1989).
3. The spores and pollen of the Potomac Group of Maryland;MARYLAND BOARD OF NATURAL RESOURCES. DEPARTMENT OF GEOLOGY, MINES AND WATER RESOURCES BULLETIN,1963
4. Brenner, G.J., Origin and Early Evolution of Angiosperms: 23 (1976).
5. BRENNER, G.J., POLLEN ET SPORES 10: 341 (1968).