Conservation of natural resources

The Holy Earth

L. H. (Liberty Hyde) Bailey

Checking the Waste

A Study in Conservation

Mary Huston Gregory

The Earth as Modified by Human Action

George P. (George Perkins) Marsh

Proceedings of the Second National Conservation Congress at Saint Paul, September 5-8, 1910

United States. National Conservation Congress

The Fight for Conservation

Gifford Pinchot

Man and Nature; Or, Physical Geography as Modified by Human Action

George P. (George Perkins) Marsh