with a_{j,k}, b_{i,k}, c_{i,j} nonnegative integers (whose maximum value implicitly bounds all variables from above). Denote by A the (lm + ln + mn) × (lmn) defining matrix of this system. Note that this matrix is generally not totally unimodular. Nonetheless, it was shown in Jesús A. De Loera, Raymond Hemmecke, Shmuel Onn, Robert Weismantel: N-fold integer programming, Discrete
