Grün, B.; Blau, J. (1997). New aspects of calpionellid biochronology: proposal for a revised calpionellid zonal and subzonal division. Revue de Paléobiologie, Genève. 16(1): 197-214.
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Grün, B.; Blau, J.
1997
New aspects of calpionellid biochronology: proposal for a revised calpionellid zonal and subzonal division