Correia, G. G., 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)”. Journal of Iberian Geology, vol. 38, vol. 38, no. 2, 2012, pp. 373-88, doi: https://doi.org/10.5209/rev_JIGE.2012.v38.n2.40464.