1. Observed Triplication of PKP
2. The fine structure of the Earth's core
3. R. C. Agrawal , 1975 . Travel times for the Indian region . Unpublished PhD thesis, Kurukshetra University, India.
4. E. P. Arnold , 1965 . The revision of seismological tables . Unpublished PhD thesis , Cambridge University.
5. Travel-times of PKP up to 145�