 Thus to obtain the space of inequivalent field strengths from the forementioned subset of integral cohomology we must quotient by these large gauge transformations.The Atiyah–Hirzebruch spectral sequence constructs twisted K-theory, with a twist given by the NS 3-form field strength, as a quotient of a subset of the cohomology with integral coefficients.In the classical limit, which corresponds to working with rational coefficients, this is precisely the quotient of a subset described above in supergravity.