  The Kolmogorov inertial range ratio of the mixed- to- longitudinal
third-order structure functions of isotropic and homogeneous turbulence is
$\frac{S_{1,2}}{S_{3,0}}=1/3$. Recent measurements by Kurien and Sreenivasan
(Phys. Rev. E {\bf 64}, 056302 (2001)), showed that, while the longitudinal
structure function was extremely close to Kolmogorov's, the measured ratio was
very far: $\frac{S_{1,2}}{S_{3,0}}\approx 0.43$. Explanation of this puzzle is
presented in this letter.
