Keller, G., C.E. Zenker, and S.M. Stone. (1989) 1989. “Late Neogene History of the Pacific-Caribbean Gateway”. Journal of South American Earth Sciences 2: 73–108. doi:10.1016/0895-9811(89)90028-x. Reference Link
Stone, S.M., and G. Keller. 1985. “Planktonic Foraminiferal Biostratigraphy of the Middle America Trench Region, Deep Sea Drilling Project Leg 84”. In Initial Reports of the Deep Sea Drilling Project. U.S. Government Printing Office. doi:10.2973/dsdp.proc.84.110.1985. Reference Link