Beltrami equations in the plane and Sobolev regularity

New results regarding the Sobolev regularity of the principal solution of the linear Beltrami equation $\bar{\partial} f = \mu \partial f + \nu \overline{\partial f}$fordiscontinuousBeltramicoefficients$\mu$and$\nu$areobtained,usingKato-Poncecommutators,obtainingthat$\overline \partial f$ belongs to a Sobolev space with the same smoothness as the coefficients but some loss in the integrability parameter. A conjecture on the cases where the limitations of the method do not work is raised.