1. Proudman, I. and W. H. Reid, Phil. Trans. Roy. Soc. (London) A247 (1954) 163.
2. Burgers, J. M., An approximate equation for the correlation function connected with a non-linear problem, Proc. of the Seventh Int. Congress of Theoretical and Applied Mechanics, Istanbul, August 1952 (not yet published at the time of writing of this paper).