Bibliography (5):

1. https://www.kurims.kyoto-u.ac.jp/~kawamura/pinwheel/paper_e.pdf

2. Bamboo Garden Trimming Problem (Perpetual Maintenance of Machines with Different Attendance Urgency Factors)

3. Bamboo Trimming Revisited: Simple Algorithms Can Do Well Too

4. Wikipedia Bibliography:

   1. NP-hardness

   2. Pinwheel scheduling  :

      https://en.wikipedia.org/wiki/Pinwheel_scheduling