Malmgren, B. A., Berggren, W. A., & Lohmann, G. P. (1983, October). Evidence for punctuated gradualism in the late Neogene Globorotalia tumida lineage of planktonic foraminifera .GeoScienceWorld, 9(3), 377-389. Abstract retrieved from http://paleobiol.geoscienceworld.org/cgi/content/abstract/9/4/377
