1. Die rhythmische Bewegungen der Kreidegeosynklinale der Ostkordillere Kolumbiens;Bürgl;Geologische Rundschau,1963
2. Zonation of the Cretaceous of central Colombia by ammonites;Etayo-Serna;Publicaciones Geológicas Especiales del Ingeominas,1979
3. Calcareous nannofossils from the Cretaceous between the North Sea and the Mediterranean;Perch-Nielsen,1979
4. Venezuela;Renz,1981