3Osterberg J O. Recent advances in load testing driven piles and drilled shafts using the Geotechnical Lecture Series [ R ]. Geotechnical Division, Illinios Section. Chicago : Amer- ican Society of Civil Engineers, 1994.
4Osterberg J O, Hayes J A. The Osterberg load cell as a research tool[C]//The 6th International Conference on Soil Mechanics and Geotechnical Engineering. Istanbul: [ s. n] ,2001.
