Discrete convexity:

• V.I. Danilov, A.V. Karzanov, and G.A. Koshevoy, Discrete strip-concave functions, Gelfand-Tsetlin patterns, and related polyhedra, J. of Combinatorial Theory, Ser.A, 112, No.2, 2005, 175-193. (Draft in ArXiv:math.CO/0404298.) [PDF] 
• A.V. Karzanov, Concave cocirculations in a triangular grid, Linear Algebra and its Appl., 400C, 2005, 67-89. (Draft in ArXiv:math.CO/0304289.) [PDF]
• A.V. Karzanov, Integer concave cocirculations and honeycombs, In: Integer Programming and Combinatorial Optimization (10th International IPCO Conference, NY, USA, June 2004, Proceedings) (Lecture Notes in Computer Sci., 3064, Springer, 2004), 368-387. (Draft in ArXiv:math.CO/0401313.) [PDF] (See also [jour])