Isolated periodic minima are unstable Antonio J. Ureña — 2006 Annales de l'I.H.P. Analyse non linéaire
A Hartman-Nagumo inequality for the vector ordinary p -Laplacian and applications to nonlinear boundary value problems. Mawhin, Jean; Ureña, Antonio J. — 2002 Journal of Inequalities and Applications [electronic only]