“…Among recent results, the method developed in the papers by Bitjukov et al [2002Bitjukov et al [ , 2003 to asymptotically solve the two-frequency two-position Markov's parabolic equation, based on the quasi-classic approximation with complex trajectories, seems to be the most general. It produces automatically other known solutions to this equation [Sreenivasiah et al, 1976;Knepp, 1983a;Oz and Heyman, 1996, 1997a, 1997b, 1997cBronshtein and Mazar, 2002]. However, even the exhaustive knowledge of the two-frequency two-position coherence functions (both, the first and second) is not sufficient to comprehensively characterize the transionospheric fluctuating channel of propagation.…”