D. Barilari, I. Beschastnyi, A. Lerario:
Volume of small balls and sub-Riemannian curvature in 3D contact manifolds
Journal of Symplectic Geometry Vol. 18, N. 2, p. 355-384, 2020

I. Beschastnyi:
Closure of the Laplace-Beltrami operator on 2D almost-Riemannian manifolds and semi-Fredholm properties of differential operators on Lie manifolds
(Preprint) 2022