Hekel, Heinz (1973): Nannofossil biostratigraphy, Leg 20, Deep Sea Drilling Project. Texas A & M University, Ocean Drilling Program, College Station, TX, United States, In: Heezen, Bruce C., MacGregor, Ian D., Foreman, Helen P., Forristall, George Z., Hekel, Heinz, Hesse, Reinhard, Hoskins, Robert H., Jones, E. John W., Krasheninnikov, Valeri, Okada, Hakuyu, Ruef, Michael H., Kaneps, Ansis G. (editor), Initial reports of the Deep Sea Drilling Project, covering Leg 20 of the cruises of the drilling vessel Glomar Challenger; Yokohama, Japan to Suva, Fiji September-November 1971, 20, 221-247, georefid:1983-028164