Izumiya, Shyuichi Kossioris, Georgios T. Semi-local classification of geometric singularities for Hamilton-Jacobi equations Mathematics Technical Report Hamilton-Jacobi equations.;Viscosity solutions. 1993-01-01
    https://kilthub.cmu.edu/articles/journal_contribution/Semi-local_classification_of_geometric_singularities_for_Hamilton-Jacobi_equations/6479465
10.1184/R1/6479465.v1