E. Indurain, E. Martín, A. Plans, y A. Rodes, «Two geometric constant for operators acting on a separable Banach space», Rev. mat. complut., vol. 1, n.º 1, p. 23, ene. 1988, doi: https://doi.org/10.5209/rev_REMA.1988.v1.n1.18176