G. Cupini, M. Guidorzi, C. Marcelli:
Necessary conditions and non-existence results for autonomous nonconvex variational problems
J. Differential Equations Vol. 243, p. 329-348, 2007

G. Cupini, M. Guidorzi, C. Marcelli:
Existence of minimizers of free autonomous variational problems via solvability of constrained ones.
Ann. Inst. H. Poincaré Anal. Non Linéaire Vol. 26, p. 1183-1205, 2009

G. Cupini, C. Marcelli:
Monotonicity properties of minimizers and relaxation for autonomous variational problems
ESAIM Control Optim. Calc. Var. Vol. 17, p. 222-242, 2011