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We use recently the next-to-next-to-leading order (NNLO)
contributions to anomalous dimension which is governing the
evolution of non-singlet quark distributions. The $xF_3$ data of
the CCFR collaboration is used to parameterize the non-singlet
parton distributions in higher order. In the fitting procedure,
Bernstein polynomial method is employed. The results of valence
quark distributions in the LO, NLO and NNLO are compered with
different theoretical models.
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