Important references
Technical background to Digital Gravelometer
Graham, D.J., Reid, I. and Rice, S.P. 2005a. Automated sizing of coarse grained sediments: Image-processing procedures. Mathematical Geology, 37(1): 1-28.
Graham, D.J., Rice, S.P. and Reid, I. 2005b. A transferable method for the automated grain sizing of river gravels. Water Resources Research, 41: W07020.
Sampling and conversion between surface/subsurface samples
Bunte, K. and Abt, S.R. 2001. Sampling Surface and Subsurface Particle-Size Distributions in Wadable Gravel- and Cobble-Bed Streams for Analyses in Sediment Transport, Hydraulics, and Streambed Monitoring. RMRS-GTR-74. US Forest Service, Rocky Mountain Research Station, Fort Collins, Colorado. http://www.fs.fed.us/rm/pubs/rmrs_gtr74.html
Church, M.A., McLean, D.G. and Wolcott, J.F. 1987. River bed gravels: sampling and analysis. In: Sediment Transport in Gravel-Bed Rivers, Thorne, C.R., Bathurst, J.C. and Hey, R.D. (eds), John Wiley and Sons, Chichester, 43-88.
Sime, L.C. and Ferguson, R.I. 2003. Information on grain sizes in gravel-bed rivers by automated image analysis. Journal of Sedimentary Research, 73: 630-636.
Grain-size statistics
Blott, S.J. and Pye, K. 2001. GRADISTAT: A grain size distribution and statistics package for the analysis of unconsolidated sediments. Earth Surface Processes and Landforms, 26(11): 1237-1248.
Folk, R.L. 1966. A review of grain-size parameters. Sedimentology, 6: 73-93.
Folk, R.L. and Ward, W.C. 1957. Brazos River bar: a study in the significance of grain size parameters. Journal of Sedimentary Petrology, 27(1): 3-26.