“…As a result, one obtains the first-order differential equation of the Riccati type (see, for example, Kunitsyn, Smorodinov, & Usachev, 1989;Pogorelov, 1990;Cui, Liang, & Wiesbeck, 1997;Titchener & Willis, 1991;Bailey, 1954). Exact and approximate analytical solutions for R can be obtained only for several profiles.…”