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2. Alpern B. Balme B. Doubinger J. Goubin N. Grebe H. Navale G. Piérart P. , 1964. La stratigraphie palynologique du Stepanien et du Permien. C. R. Congr. Avanc. Ãtud. Stratigr. Carb., Paris (1963), Pt. 3, 1119â29.
3. Megaspores from the Michigan coal basin;Arnold;Contr. Mus. Paleont. Univ. Mich.,1950
4. The spore genera from the Upper Carboniferous coals of the Saar and their value in stratigraphical studies;Bhardwaj;Palaeobotanist,1955
5. The palynological investigations of the Saar coals (Part 1âMorphography of sporae dispersae);Bhardwaj;Palaeontographica,1957