1. M. Christ, Endpoint bounds for singular fractional integral operators, UCLA preprint (1988).
2. D. V. Cruz Uribe and A. Fiorenza, Variable Lebesgue Spaces. Foundations and Harmonic Analysis, Birkhäuser/Springer (Heidelberg, 2013).
3. E. Ferreyra, T. Godoy and M. Urciuolo, Lp−Lq estimates for convolution operators with n-dimensional singular measures, J. Fourier Anal. Appl., 3 (1997), 475–484.
4. E. Ferreyra, T. Godoy and M. Urciuolo, Endpoint bounds for convolution operators with singular measures, Colloq. Math., 76 (1998), 35–47.
5. W. Littman, Lp−Lq estimates for singular integral operators arising from hyperbolic equations, in: Partial Differential Equations (Proc. Sympos. Pure Math., vol. 23, Univ. California, Berkeley, 1971), Amer. Math. Soc. (Providence, RI, 1973), pp. 479–481.