1. Hansen, A. G., Similarity Analysis of Boundary Value Problems in Engineering, 1st ed.Prentice-Hall, 1964, pp.9-30.
2. Structure of trailing vortices.
3. Sokolnikoff, I. S. and Sokolnikoff, E. S., Higher Mathematics for Engineers and Physicists, 2nd ed.McGraw-Hill, New Yorkand London,1941, pp.86-91.