[1] D. W. Trainor el al., Appl. Phys. Lett., 33(7), 648 (1978)

[2] Ding CheDgmao, Physica В & С (3), 396 (1984)

[3] A. Ν. Nesmeyanov "Vapor Press urе of the Elements" (Acad. Nauk SSSR, Moscow, 1961)

[4] Stanley Bashkin et al., "Atomic energy level and grotrian diagrams" (Vol. II, North-Hoi land Publishing Сопфапу, Amsterdam, New Yorkj 1978), p. 340