@misc{indiciae4ed235f5de06,
  title = {Programmed random time interval signalling device.},
  author = {E F Keen and P J Calver},
  year = {1969},
  doi = {10.1088/0022-3735/2/10/420},
  url = {https://pubmed.ncbi.nlm.nih.gov/5343470/},
  note = {Source identifier: 5343470}
}