Jaker, Ali Sk., and N.D. Chakraborty-sk. “On Strongly Pettis Integrable Functions in Locally Convex Spaces”. Revista Matemática Complutense, vol. 6, no. 2, Jan. 1993, p. 241, https://doi.org/10.5209/rev_REMA.1993.v6.n2.17818.