@misc{indiciae173b142149a8,
  title = {Periodic solutions to nonautonomous difference equations.},
  author = {M E Clark and L J Gross},
  year = {1990},
  doi = {10.1016/0025-5564(90)90057-6},
  url = {https://pubmed.ncbi.nlm.nih.gov/2134487/},
  note = {Source identifier: 2134487}
}