Source: https://www.researchgate.net/profile/Frederic-Elie-2/publication/316669656_Suites_de_Cauchy_et_theoreme_du_point_fixe_de_Banach/links/590b4a530f7e9b1d082726c1/Suites-de-Cauchy-et-theoreme-du-point-fixe-de-Banach.pdf