1. Soluzione periodiche di equazioni a derivate parziali di tipo iperbolico non lineari;de Simon,1968
2. Recent trends in nonlinear boundary value problems;Mawhin,1977
3. VII. Intern. Konferenz über nichtlineare Schwingungen,1977
4. Characterizations of the ranges of some nonlinear operators and applications to boundary value problems;Brézis;Ann. Scuola Norm. Sup. Pisa, cl. Sci.,1978