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4. Arnold, V. I.: Normal forms of functions near degenerate critical points, Weyl groupsA k ,D k ,E k and lagrange singularities. Funct. Anal. and appl.6, N4 254?272 (1972)
5. Arnold, V.I.: Classification of unimodular critical points of functions. Funct. Anal. and appl.7, N3 75?76 (1973)