Richard D. Barksdale
R. N. Swamy
Department of the Environment Staff Great Britain
Leonid Dvorkin
B. F. Arbogast
S. E. Yundt
Unknown Author
Robert Whelan
Sand & Gravel Association National Stone
Canada. Indian and Northern Affairs Canada
Ralph S. Mason
S. Chandra
L. R. Arnold
Great Britain. Advisory Committee on Aggregates.