The paper analyzes some variational problems of plastic deformation theory with graded hardening.
Crosta, G. (1994). Mathematical Review: MR1202731 Serëgin, G. A. On the regularity of minimizers of some variational problems in the theory of plasticity. (Russian) Algebra i Analiz 4 (1992), no. 5, 181--218; translation in St. Petersburg Math. J. 4 (1993), no. 5, 989–1020. MATHEMATICAL REVIEWS, 94e, 49015-49015.