1. R. V. Lokutsievskiy and Yu. L. Sachkov, “Liouville integrability of sub-Riemannian problems on Carnot groups of step 4 or greater,” Sb. Math. 209 (5), 672–713 (2018).
2. A. A. Agrachev and Yu. L. Sachkov, Control Theory from the Geometric Viewpoint (Springer, Berlin, 2004).
3. A. Agrachev, D. Barilari, and U. Boscain, A Comprehensive Introduction to Sub-Riemannian Geometry from Hamiltonian Viewpoint (Cambridge Univ. Press, Cambridge, 2019).
4. I. A. Bizyaev, A. V. Borisov, A. A. Kilin, and I. S. Mamaev, “Integrability and nonintegrability of sub-Riemannian geodesic flows on Carnot groups,” Regular Chaotic Dyn. 21 (6), 759–774 (2016).
5. E. Cartan, “Lès systemes de Pfaff a cinque variables et lès equations aux derivees partielles du second ordre,” Ann. Sci. Ec. Norm. 27 (3), 109–192 (1910).