Cocho, G., A. Mondragon, and M. Colon-Vela. “Euclidean Expansion of the Scattering Amplitude in Nuclear Physics”. Revista Mexicana De Física, vol. 17, no. 1, Jan. 1968, pp. 59-67, https://rmf.smf.mx/ojs/index.php/rmf/article/view/910.