9[1]P. Barkan et al. Development of contact materials for vacuum interrupters [J ]. IEEE Trans. Power, Apparatus and Systems. 1971, Vol. PAS - 90 (1) :350-359.
10[4]P. Frey et al. Investigations on the release of gas fromcontact materials for vacuum switching devices during operation, Proc 11th Intl. Conf. on Electric Contacts (pub, VDE-Verlag GmbH. Berlin). 1992 :317-320.