1. The Neogene: Part 2: Neogene geochronology and chronostratigraphy Berggren, William A.; Kent, Dennis V.; Van Couvering, John A. 1985 Articles GeophysicsPaleontology
2. What, if anything, is Quaternary? Van Couvering, John A.; Berggren, William A.; Aubry, Marie-Pierre; Gradstein, Felix M.; Kent, Dennis V.; Hilgen, Frits J.; Lourens, Lucas J.; McGowran, Brian 2009 GeologyPaleontologyPaleoclimatology