1. B. A. Dubrovin, A. S. Fokas and P. M. Santini, “Inverse Spectral Transform and the Solution of Certain Nonlinear Algebraic Equations”, Preprint Dipartimento di Fisica, Università di Roma I, 1991.
2. G. Springer, Introduction to Riemann surfaces, Addison Wesley, (1957).
3. B. A. Dubrovin, Func. Anal. Appl., 11, 265 (1977).
4. P. M. Santini, Inverse Problems, 6, 665 (1990).
5. M. Bruschi and F. Calogero, SIAM J. Math. Anal. 21 (1990).