1. Akhatov, I.S., Gazizov, R.K., Ibragimov, N.K.: Group classification of equation of nonlinear filtration. Dokl. AN SSSR 293, 1033–1035 (1987)
2. Akhatov, I.S., Gazizov, R.K., Ibragimov, N.K.: Nonlocal symmetries. A heuristic approach. In: Itogi Nauki i Tekhniki, Current Problems in Mathematics. Newest Results, vol. 34, pp. 3–83. VINITI, Moscow (1989). (in Russian, English translation in J. Sov. Math. 55, 1401–1450 (1991))
3. Anco, S.C., Bluman, G.: Nonlocal symmetries and nonlocal conservation laws of Maxwell’s equations. J. Math. Phys. 38, 3508–3532 (1997)
4. Anco, S.C., Bluman, G.: Direct construction method for conservation laws of partial differential equations I. Examples of conservation law classifications. Eur. J. Appl. Math. 13(5), 545–566 (2002); arXiv:math-ph/0108023
5. Anco, S.C., Bluman, G.: Direct construction method for conservation laws of partial differential equations II. General treatment. Eur. J. Appl. Math. 13(5), 567–585 (2002); arXiv:math-ph/0108024