On the Application of a Statistical Approximation to the Theory of Turbulent Diffusion P. Roberts Indiana University Mathematics Journal 1957 text pdf 10.1512/iumj.1957.6.56043 10.1512/iumj.1957.6.56043 en Indiana Univ. Math. J. 6 (1957) 781 - 799 state-of-the-art mathematics http://iumj.org/access/