Manuel Bodirsky Gustav Nordh Timo von Oertzen Integer programming with 2-variable equations and 1-variable inequalities. 572-575 2009 109 Inf. Process. Lett. 11 http://dx.doi.org/10.1016/j.ipl.2009.01.025 db/journals/ipl/ipl109.html#BodirskyNO09