1. Coal Assessment;Mott,1947
2. Stratigraphy and paleobotany of the Golden Valley Formation (early Tertiary) of western North Dakota;Hickey;Geol. Soc. Amer. Memoir,1977
3. Palynology of the Hagel lignite bed and associated strata, Sentinel Butte Formation (Paleocene) in central North Dakota;Steadman;M.A. Thesis, University of North Dakota, Grand Forks, ND,1985
4. Palynology of Gulf Coast lignites: the stratigraphic framework and depositional environments;Elsik,1978
5. Modern and ancient pollen sedimentation around tree islands in the Okefenokee swamp;Rich;Palynology,1979