However, this does not fix the period issue, which depends on the low bits of the modulus. Fortunately, the Montgomery reduction algorithm permits other moduli, as long as they are relatively prime to the base "b", and this can be applied to permit a modulus of the form "arbr"−"a"0, for a wide range of values "a"0. Goresky and Klapper developed the theory of these generalized multiply-with-carry generators, proving, in particular, that choosing a negative "a"0 and "ar"–"a"0 < "b" the carry value is always smaller than "b", making the implementation efficient. The more general form of the modulus improves also the quality of the generator, albeit one cannot always get full period.