Integer and Mixed-Integer Programming Problems
A hard mixed integer problem in LP format contributed by D. Bienstock,
z_ij variables are 0-1 (56 total), all other variables are continuous
Mixed Integer Programming problem library, see R.E. Bixby, E.A. Boyd, and
R.R. Indovina: MIPLIB: A Test Set of Mixed Integer Programming Problems,
SIAM-News 25, 2 (1992), p.16.
General 0/1 Integer Programming (Multiple Knapsack) problems contributed
by J. Heitkötter.