Robertson, I., Wils, T. H., Eshetu, Z., Sass-Klaassen, U. G., & Koprowski, M. (2009). Periodicity of growth rings in Juniperus procera from Ethiopia inferred from crossdating and radiocarbon dating. Dendrochronologia, 27(1), p. 45. doi:10.1016/j.dendro.2008.08.002

Robertson, Iain, Tommy H.G Wils, Zewdu Eshetu, Ute G.W Sass-Klaassen, and Marcin Koprowski. "Periodicity of Growth Rings in Juniperus Procera From Ethiopia Inferred From Crossdating and Radiocarbon Dating." Dendrochronologia 27, no. 1 (2009): 45.

Robertson, Iain, et al. "Periodicity of Growth Rings in Juniperus Procera From Ethiopia Inferred From Crossdating and Radiocarbon Dating." Dendrochronologia 27.1 (2009): 45.