Gray D., Stiles J. M., Celik I. Final Report on Theoretical and numerical studies of constitutive relations for frictional granular flow. 1991. Morgantown Energy Technology Center Morgantown, WV, USA, West Virginia University Morgantown, WV, USA: DOE/MC/24207-3009; ON: DE91002089. p. 168. http://dx.doi.org/10.2172/5119247.