1. Signorini A.,Sopra alcune questioni di elasto-statica. Atti Soc. Ital per il Progresso delle Scienze, (1933).
2. Fichera G.,Boundary value problems of Elasticity with unilateral constraints, Encl. of Physics, vol. VI a/2, Springer-Verlag (1972).
3. Duvaut G., Lions J.L.,Les inéquations en mécanique et en physique, Dunod, Paris (1972).
4. Stampacchia G.,Variational inequalities, Pubbl. IAX, s. III, 25, Roma, (1969).
5. Weitsmann Y.,On the unbounded contact between plates and an elastic half-space, Jour. Appl. Mech., 36, pp. 198–202, (1969).