  We compute the color-planar and complete light quark non-singlet
contributions to the heavy quark form factors in the case of the axialvector,
scalar and pseudoscalar currents at three loops in perturbative QCD. We
evaluate the master integrals applying a new method based on differential
equations for general bases, which is applicable for all first order
factorizing systems. The analytic results are expressed in terms of harmonic
polylogarithms and real-valued cyclotomic harmonic polylogarithms.
