Vasil Genchev, and Vasil Genchev. β€œIs It Time for a Rocket Engine for Pile Driving Hammers?”. Global Journals of Research in Engineering 13, no. G4 (May 15, 2013): 7–16. Accessed April 30, 2024. https://engineeringresearch.org/index.php/GJRE/article/view/895.