Pascal Tessy, The 'Proboscidean Datum Event': How Many Proboscideans and How Many Events?, in European Neogene Mammal Chronology, NATO ASI Series (Series A: Life Sciences), vol. 180, Springer, 1990, pp. 237–252, DOI:10.1007/978-1-4899-2513-8_16, ISBN978-1-4899-2513-8.