@misc{indiciae2551dc4adcfc,
  title = {Direct-space methods in phase extension and phase refinement. VI. PERP (phase extension and refinement program).},
  author = {L S Refaat and C Tate and M M Woolfson},
  year = {1996},
  doi = {10.1107/s0907444996008463},
  url = {https://pubmed.ncbi.nlm.nih.gov/15299572/},
  note = {Source identifier: 15299572}
}