1. Poleward migration of early angiosperm floras;Axelrod;Science,1959
2. The spores and pollen of the Potomac Group of Maryland;Brenner;Dept. Geol., Mines, Water Resources Maryland, Bull.,1963
3. Evidence of a possible gymnospermous origin of Tricolpites troedssonii Erdtman;Couper;New Phytologist,1956
4. British Mesozoic microspores and pollen grains;Couper;Palaeontographica, B,1958
5. The morphological basis for Paleozoic origin of angiosperms;Eames,1959