A New Proof for Maximal Monotonicity of Subdifferential Operators

We present a new proof for maximal monotonicity of subdifferential operators. This result was originally proved by R. T. Rockafellar [Pacific J. Math. 33 (1970) 209–216] where other fundamental results were also proved. The proof presented here is simpler and makes use of classical results from subdifferential calculus as Brøndsted-Rockafellar's theorem and Fenchel duality formula.