1. E. A. Gulbranson, K. F. Andrew, P. E. Blackburn, T. P. Copan and A. Merlin: WADD TR 59-575, Astia 236599, Feb. 1960.
2. North American Aviation Corp., Astia 147839, Sept. 1957.
3. M. G. Cowgill and J. Stringer, J. Less Common Metals, vol. 2 1960, pp. 233–240.