Perch-Nielsen 1979. Calcareous nannofossil zonation at the Cretaceous/Tertiary boundary in Denmark. Birkelund, T.; Bromley, R.G.[Eds]. Cretaceous-Tertiary boundary events. Symposium, Copenhagen, September 1979. 1. The Maastrichtian and Danian of Denmark., University of Copenhagen, Copenhagen, 1979: 74-77. Chapter pagination: 115-135