1. Ervin . R. D. ,et al. “ The Yaw Stability of Tractor-Semitrailers During Cornering .” Final Report, Contract No. DOT-HS-7-01602 . Highway Safety Research Institute, University of Michigan . Ann Arbor . June 1979 .
2. Gillespie , T. D. , Sayers , M. W. and Segel , L. “ Calibration of Response-Type Road Roughness Measuring Systems .” Final Report No. 228. NCHRP Project 1-18 , Highway Safety Research Institute, The University of Michigan , Ann Arbor , December 1980 .