- Davide Barilari, Stefan Ivanov, “A Bonnet–Myers type theorem for quaternionic contact structures”, Calc. Var., 58, № 1, 2019, 37
- Andrei A. Agrachev, 1932, Nonlinear and Optimal Control Theory, 2008,
1 - Andrei Agrachev, Paul W. Y. Lee, “Generalized Ricci curvature bounds for three dimensional contact subriemannian manifolds”, Math. Ann., 360, № 1-2, 2014,
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