Phosphate rock.

Author:	Johnson, Bertrand Leroy,
Year:	1930
Document Type:	USBI
Issuing Agency:	Dept. of Commerce, U.S. Bureau of Mines,
SUDOC:	I 28.27:6256
Series:	Information circular / Bureau of Mines ;
Report Number:	6256
Subject:	Phosphate rock
Link:	https://hdl.handle.net/2027/mdp.39015077576133