Sherma, Y. P., A. K. Singhvi, D. P. Agrawal, B. Gaulin, and F. T. Hedgcock. “Physical Research Laboratory TL Dates - 1981 (II)”. Ancient TL, vol. 5, no. 2, Mar. 1981, pp. 6-8, doi:10.26034/la.atl.1981.047.