1. V. P. Maslov, Perturbation Theory and Asymptotic Methods (Izd. Mosk. Univ., Moscow, 1965) [in Russian].
2. V. P. Maslov and M. V. Fedoryuk, Semiclassical Approximation for Equations of Quantum Mechanics (Nauka, Moscow, 1976) [in Russian].
3. Wolfram Mathematica, www.wolfram.com.
4. S. Yu. Dobrokhotov, V. E. Nazaikinskii, and A. I. Shafarevich, “New integral representations of the Maslov canonical operator in singular charts,” Izv. Math. 81 (2), 286–328 (2017).
5. V. I. Arnol’d, A. N. Varchenko and S. M. Gusein-Zade, Singularities of Differentiable Mappings, Vol. 1: Classification of Critical Points, Caustics, and Wave Fronts (Nauka, Moscow, 1982) [in Russian].