Hofker, J. (1966). Maestrichtian, Danian and Paleocene Foraminifera. The Foraminifera of the type-Maestrichtian in South Limburg, Netherlands, together with the Foraminifera of the underlying Gulpen Chalk and the overlying calcareous sediments; the Foraminifera of the Danske Kalk and the overlying greensands and clays as found in Denmark. Palaeontographica, Supplementbände. 10: 1-376.
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Hofker, J.
1966
Maestrichtian, Danian and Paleocene Foraminifera. The Foraminifera of the type-Maestrichtian in South Limburg, Netherlands, together with the Foraminifera of the underlying Gulpen Chalk and the overlying calcareous sediments; the Foraminifera of the Danske Kalk and the overlying greensands and clays as found in Denmark