Potrykus, A. . (2009): «A Symbolic Calculus and a Parametrix Construction for Pseudodifferential Operators with Non-Smooth Negative Definite Symbols», Revista Matemática Complutense, 22(1), pp. 187–207. doi: https://doi.org/10.5209/rev_REMA.2009.v22.n1.16347.