1. E. Lehfeld,Ultrasonics 10 (1967) 219.
2. W. B. Tarpley andK. Kartluke, US, Aeroprojects Inc., AEC NYO-10005 (1961) and NYO-9587 (1961).
3. O. Dragan andA. Protopopescu, “in Proceeding of the 1st Symposium on High Power Ultrasonics” 17–19 September 1970 (IPC Science and Technology Press 1972) p. 109.
4. K. Siwkiewicz andS. Stoeatz,Powder Metall. Int. 18 (1986) 6.
5. B. Rogeaux andP. Boch,J. Mater. Sci. Lett. 4 (1985) 403.