Phosphate rock(in two parts) :

Author:	Waggaman, William H.
Additional Authors:	Ruhlman, E. Robert.
Year:	1960
Document Type:	USBI
Issuing Agency:	Bureau of Mines,
SUDOC:	I 28.27:7951
Series:	Information circular ;
Report Number:	7951
Subject:	Phosphate industry--United States
Link:	https://hdl.handle.net/2027/mdp.39015078461095