5Webster, S. L. , R. H. Grau, and R. P. Williams. “Descripion and Application of Dual Mass Dynamic Cone Penetrometer, “ U. S. Army Engineer Waterways Experiment Station. Instruction Report,No. GL -92 -3(1992).
6Webster SL, Grau R H, Williams R P. Description and application of dual mass dynamic cone penetrometer [ R ]. U. S. Army Engineer Waterways Experiment Station, Instruction Report, No. GL-92-3, 1992.