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We derive the Kramers-Moyal equation for the conditional
probability density of velocity increments from the theoretical
model recently proposed by V. Yakhot [Phys. Rev. E {\bf 57}, 1737
(1998)] in the limit of the high Reynolds number. We show that the
higher order $(n\geq 3)$ Kramers-Moyal coefficients tend to zero
and the velocity increments are evolved by the Fokker-Planck
operator. Our result are compatible with the phenomenological
description, developed for explaining recent experiments by R.
Friedrich and J. Peinke.
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