1. S. Lie, Theorie der Transformationsgruppen, 3 vols. (originally published in Leipzig, 1888, 1890, 1893). Second Edition, Chelsea, New York (1970).
2. S. Lie, Uber die Integration durch bestimmte Integrale von einer Klasse linearer partieller Differentialgleichungen, Arch. für Math., Vol. VI, No. 3, Kristiana, p. 328 (1881).
3. L.V. Ovsiannikov, Group analysis of differential equations (in Russian) Nauka, Moscow 1978. English edition, Academic Press, New York (1982).
4. W.F. Ames, Nonlinear partial differential equations in engineering, Vol. II, Academic Press, New York (1972).
5. V.V. Puhnachev, Group properties of the equations of Navier-Stokes in the plane, Journal of Appl. Mech. and Tech. Phys. 1 (1960) 83–90 (in Russian).