Salomon B. Kroonenberg, Jos G.M. Bakker, and A. Marian van der Wiel. “Late Cenozoic Uplift and Paleogeography of the Colombian Andes: Constraints on the Development of High-Andean Biota”. Netherlands Journal of Geosciences, Jan. 1990, pp. 279-90, https://njgjournal.nl/index.php/njg/article/view/12870.