1. Invariante Variationsprobleme;Noether;Nachr. K. Ges. Wiss. Göttingen, Math.-Phys. Kl.,1918
2. Invariant variation problems
3. Invariant Variational Principles;Logan,1977
4. Applications of Lie Groups to Differential Equations;Olver,1986
5. Symmetries and Differential Equations;Bluman,1989