@misc{indiciae0d798a35c91c,
  title = {Vela X-1 pulse timing. II - Variations in pulse frequency},
  author = {Deeter, J. E. and Boynton, P. E. and Lamb, F. K. and Zylstra, G.},
  year = {1989},
  url = {https://ntrs.nasa.gov/citations/19890035332},
  note = {Source identifier: 19890035332}
}