Stability of Equilibria for the $ mathfrak{so}(4)$ Free Rigid Body. - Petre Birtea; Ioan Casu; Tudor S. Ratiu; Murat Turhan (J. Nonlinear Sci., 2012)

The stability problem and special solutions for the 5-components Maxwell-Bloch equations. - Petre Birtea; Ioan Casu (Appl. Math. Lett., 2013)

Energy Methods in the stability Problem for the 픰픬(4) Free Rigid Body. - Petre Birtea; Ioan Casu (Int. J. Bifurc. Chaos, 2013)

First order optimality conditions and steepest descent algorithm on orthogonal Stiefel manifolds. - Petre Birtea; Ioan Casu; Dan Comanescu (Optim. Lett., 2019)