Analytic Perturbation Theory and Renormalization Scheme Dependence in   Tau Decay
  We apply analytic perturbation theory in next-to-next-to-leading order to inclusive semileptonic $\tau$-decay and study the renormalization scheme dependence. We argue that the renormalization scheme ambiguity is considerably reduced in the analytic perturbation theory framework and we obtain a rather stable theoretical prediction. 
K. A. Milton, I. L. Solovtsov, and V. I. Yasnov