Periodic solutions for a class of Lorenz-lagrangian systems J. F. Toland — 1988 Annales de l'I.H.P. Analyse non linéaire
A Riemann–Hilbert problem and the Bernoulli boundary condition in the variational theory of Stokes waves E. Shargorodsky; J. F. Toland — 2003 Annales de l'I.H.P. Analyse non linéaire