1. P. Blum, F. Bertaut, Acta Crystallogr. 7, 81 (1954)
2. V.I. Matkovich, J. Economy, R.F. Giese, R. Barrett, Acta Crystallogr. 19, 1056 (1965)
3. Yu.B. Kuzma, Yu.Y. Voroshilov, Sov. Phys. Cristallogr. 12, 297 (1967)
4. Yu.B. Kuzma, P.I. Kripyakevich, N.S. Bilonishko, Dopov. Akad. Nauk. Ukr. RSR A10, 939 (1969)
5. Yu.B. Kuzma, Sov. Phys. Cristallogr. 15, 312 (1970)