Publisher
Springer Science and Business Media LLC
Subject
General Physics and Astronomy
Reference4 articles.
1. F. González-Gascón:Lett. Nuovo Cimento,19, 366 (1977).
2. R. Hermann:Differential Geometry and the Calculus of Variations (New York, N. Y., 1968), p. 63.
3. I. G. Pretrovskii:Partial Differential Equations (London, 1967), p. 19.
4. F. González-Gascón andA. González-López:Lett. Nuovo Cimento,32, 353 (1981).