Stability of Relative Equilibria in the Problem of N+1 Vortices. - Hildeberto E. Cabral; Dieter S. Schmidt (SIAM J. Math. Anal., 2000)

Nonlinear Stability of a Latitudinal Ring of Point-Vortices on a Nonrotating Sphere. - Hildeberto E. Cabral; Stefanella Boatto (SIAM J. Appl. Math., 2003)