@Article{ cupguimar07, author = { Cupini, Giovanni and Guidorzi, Marcello and Marcelli, Cristina }, title = { Necessary conditions and non-existence results for autonomous nonconvex variational problems }, journal = { J. Differential Equations }, year = { 2007 }, volume = { 243 }, pages = { 329-348 }, URL = { http://cvgmt.sns.it/paper/586/ }, note = { cvgmt preprint} }