We prove that a maintenance problem on frequency-constrained maintenance jobs with a hierarchical structure is integer-factorization hard. This result holds even on simple systems with just two components to maintain. As a corollary, we provide a first hardness result for Levi et al.'s modular maintenance scheduling problem (Naval Research Logistics 61, 472-488, 2014).

翻译：我们证明，具有层次结构的频率约束维护作业的维护问题是整数分解难的。这一结论即使在仅有两个组件需要维护的简单系统中也成立。作为推论，我们给出了Levi等人模块化维护调度问题（《海军研究物流》61, 472-488, 2014）的首个困难性结果。