Mihlbachler, K., Kollmann, T., Seidel-Morgenstern, A., Tomas, J., & Guiochon, G. (1998). Measurement of the degree of internal friction of some packing materials. Journal of Chromatography A, 818(2), 155-168. doi:10.1016/S0021-9673(98)00546-9.