  In this paper we study the long-standing open question regarding the
computational complexity of one of the core problems in supply chains
management, the periodic joint replenishment problem. This problem has received
a lot of attention over the years and many heuristic and approximation
algorithms were suggested. However, in spite of the vast effort, the complexity
of the problem remained unresolved. In this paper, we provide a proof that the
problem is indeed strongly NP-hard.
