Progress report :
experiments on strength of small pillars of coal in the Pittsburgh bed /
by H.P. Greenwald, H.C. Howarth, and Irving Hartmann.

APA Citation

Greenwald, H. P. (Harold Putnam)., Hartmann, I., Howarth, H. C. (1941). Progress report: experiments on strength of small pillars of coal in the Pittsburgh bed. [Washington, D.C.]: U.S. Dept. of the Interior, Bureau of Mines.

MLA Citation

Greenwald, H. P. (Harold Putnam), 1893-, Irving Hartmann, and H. C Howarth. Progress Report: Experiments On Strength of Small Pillars of Coal In the Pittsburgh Bed. [Washington, D.C.]: U.S. Dept. of the Interior, Bureau of Mines, 1941.

Warning: These citations may not always be complete (especially for serials).