Perusset André. 1983. Oro-Hydrographie(Le Relief) in led by The Ministère de l'Education Nationale de la Republique Gabonaise. Pg 10-13. Paris, France: Edicef. Petringa, Maria. . Bloomington, IN: AuthorHouse, 2006. ISBN 978-1-4259-1198-0. Describes Pierre Savorgnan de Brazza's extensive explorations of the Ogoué River basin.