1. S. Sokolov, USSR Patent No. 49 (August 1936), British Patent No. 477139(1937), and U.S. Patent No. 21 64 125(1939).
2. J.E. Jacobs, “Ultrasonic Image Converter Systems Utilizing Electron-Scanning Techniques,” IEEE Trans. Sonics Ultrason. SU-15 146–152(1968).
3. B.A. Auld, R.J. Gilbert, K. Hyllested, C.G. Roberts, and D.C. Webb, “A 1.1 GHz Scanned Acoustic Microscope,” in Acoustical Holography, edited by G.Wade (Plenum. N.Y., 1972), Vol.4, pp. 73–96.
4. K. Wang, H. Shen and G. Wade, “An Opto-Acoustic Transducer for High-Sensitivity Ultrasonic Imaging” Proc. 1975 Ultrasonics Sumposium Cat. No. 75-CHO-994-4SU. IEEE New York, NY 10017
5. R. Pohlman, “Material Illumination by Means of Acoustic-Optical Imagery,” Z. Phys. 1133 697(1939).