KITAZAWA, Naoki. On Reeb graphs induced from smooth functions on 3-dimensional closed manifolds with finitely many singular values. Topological Methods in Nonlinear Analysis. Online. 12 June 2022. Vol. 59, no. 2B, pp. 897 - 912. [Accessed 22 July 2024]. DOI 10.12775/TMNA.2021.044.