Ortiz-López, J., and R. Gómez-Aguilar. “Dielectric Permittivity and AC Conductivity in Polycrystalline and Amorphous $\pmb{C_{60}}$”. Revista Mexicana De Física, vol. 49, no. 6, Jan. 2003, pp. 529-0, https://rmf.smf.mx/ojs/index.php/rmf/article/view/3206.