4) Y. F. Zheng, L. C. Zhao and H. Q. Ye: Mat. Sci. Eng. A273-275(1999) 271-274.
5) J. V. Humbeek and G. Firstov: On Advanced Materials Processing, The Fourth Pacific Rim Intl. Conf. (PRICM-4), ed. by S. Hanada, Z. Zhong, S. W. Nam and R. N. Wright, (The Jpn. Inst. Metals, 2001), Vol. 2, 1871-1874.