G. G. Correia, L. V. Duarte, A. Pereira, and R. L. Silva, “Outcrop gamma-ray spectrometry: Applications to the Sinemurian–Pliensbachian organic-rich facies of the Lusitanian Basin (Portugal)”, JIGE, vol. 38, no. 2, pp. 373–388, Nov. 2012, doi: https://doi.org/10.5209/rev_JIGE.2012.v38.n2.40464