AIMAR, H.; GÓMEZ, I.; IAFFEI, B. Maximal Function Estimates for the Parabolic Mean Value Kernel. Revista Matemática Complutense, v. 21, n. 2, p. 519–527, 15 jul.2008 https://doi.org/10.5209/rev_REMA.2008.v21.n2.16412.