A. . Favini, R. . Labbas, K. . Lemrabet, y B.-k. . Sadallah, «Study of a Complete Abstract Differential Equation of Elliptic Type with Variable Operator Coefficients, I», Rev. mat. complut., vol. 21, n.º 1, pp. 89–133, abr. 2008, doi: https://doi.org/10.5209/rev_REMA.2008.v21.n1.16438