 However the MMS prescription for calculating twisted K-theory is easily S-covariantized, as the Freed-Witten anomalies respect S-duality.Thus the S-covariantized form of the MMS construction may be applied to construct the S-covariantized twisted K-theory, as a set, without knowing having any geometric description for just what this strange covariant object is.This program has been carried out in a number of papers, such as and , and was also applied to the classification of fluxes by .