1. E. Mauceli et al., The Allegro gravitational wave detector: Data acquisition and analysis. Phys. Rev. D 54(2), 1264–1275 (1996)
2. M. McHugh et al., Calibration of the ALLEGRO resonant detector. Classical Quant. Grav. 22(18), S965–S973 (2005)
3. A.G. Bodine Jr., Sonic method and apparatus for driving casings through earthen formations, U.S. Pat. No. 3,375,884 (Apr. 2, 1968)
4. M. Janes, Sonic Pile Driving: The history and the resurrection of vibration free pile driving, http://www.resonancetechnology.ca/res%20driver%20history%20090112.pdf . A very impressive video comparing the resonant and drop hammer techniques is also available from that site: http://www.resonancetechnology.ca/gallery%20video%201.php
5. A.G. Bodine Jr., Sonic method and apparatus for grinding rock material and the like to powder, U.S. Pat. No. 3,429,512 (Feb. 25, 1969)