[1] Alberti G, Ambrosio L, Cannarsa P. On the singularities of convex functions. Manuscripta Math, 1992, 76}:421-435
[2] Ambrosio L, Fusco N, Pallara D. Functions of Bounded Variation and Free Discontinuity Problems. Oxford:Clarendon Press, 2000
[3] Aubin J, Frankowska H. Set-Valued Analysis//Tamer B. Systems and Control:Foundations and Applications. Boston:Basel, 1990:205-264
[4] Evans L, Gariepy R. Measure Theory and Fine Properties of Functions. Boca Taton:CRC Press, 1991
[5] Federer F. Geometric Measure Theory. New York:Springer, 1969
[6] Giaquinta M, Modica G, Sou?ek J. Graphs of finite mass which cannot be approximated in area by smooth graphs. Manuscripta Math, 1993, 78}:259-271
[7] Giaquinta M, Modica G, Sou?ek J. Cartesian Currents in the Calculus of Variations, I, II. Berlin:Springer-Verlag, 1998
[8] Miranda M. Superfici cartesiane generalizzate ed insiemi di perimetro localmente finito sui prodotti cartesiani. Annali della Scuola Normale Superiore di Pisa-Classe di Scienze, 1964, 18:515-542
[9] Mucci D. Approximation in area of graphs with isolated singularities. Manuscripta Math, 1995, 88}:135-146
[10] Mucci D. Approximation in area of continuous graphs. Calc Var, 1996, 4:525-557
[11] Mucci D. Graphs of finite mass which cannot be approximated by smooth graphs with equibounded area. J Func Anal, 1998, 152}:467-480
[12] Mucci D. A characterization of graphs which can be approximated in area by smooth graphs. J Eur Math Soc, 2001, 3:1-38
[13] Rockafellar R. Convex Analysis. Princeton:Princeton University Press, 1997
[14] Stein E, Shakarchi R. Real Analysis:Measure theory, Integration, and Hilbert spaces. Princeton:Princeton University Press, 2009