During the past eighteen months discussions have been held with the Anthracite Producers Association on the desirability of altering and introducing a second and possibly a third grade.
Reference:
Savage, W. 1965. Anthracite grading. http://hdl.handle.net/10204/13040 .
Savage, W. (1965). Anthracite grading Retrieved from http://hdl.handle.net/10204/13040