1. Al'shits, V.I., Lothe, J.: Elastic waves in triclinic crystals. I. General theory and the degeneracy problem. Kristallografiya24, 672–683 (1979); Al'shits, V.I., Lothe, J.: Elastic waves in triclinic crystals. II. Topology of polarization fields and some general theorems. Kristallografiya24, 683–693 (1979)
2. Arnold, V.I.: Remarks on the stationary phase method and the Coxeter numbers. Russ. Math. Surv.28, No. 5, 19–48 (1973)
3. Arnold, V.I.: Wave front evolution and equivariant Morse lemma. Comm. Pure and Appl. Math.29, 557–582 (1976)
4. Arnold, V.I.: Surfaces defined by hyperbolic equations. Math. Zam.44, 3–18 (1988)
5. Arnold, V.I.: On the interior scattering of waves defined by hyperbolic variational principles. J. Geom. Phys.5, 305–315 (1988)