1. B.W. Roberts, NBS Technical Note 983 (1978).
2. K. Tachikawa, Filamentary A15 Superconductors, edited by M. Suenaga and A. F. Clark, Plenum Press, NY (1980), p. 1.
3. H. Hillmann, H. Pfister, E. Springer, M. Wilhelm and K. Wohlleben, idem.
4. J. A. Lee and C. A. Scott, idem.
5. E. Gregory, E. Adam, W. Marancik, P. Sanger, and C. Spencer, idem.