APA-referens (7:e uppl.)
Hays, S. P. (1999). Conservation and the gospel of efficiency: The progressive conservation movement, 1890-1920. University of Pittsburgh Press.
Chicago-referens (17:e uppl.)
Hays, Samuel P. Conservation and the Gospel of Efficiency: The Progressive Conservation Movement, 1890-1920. Pittsburgh, Pennsylvania: University of Pittsburgh Press, 1999.
MLA-referens (9:e uppl.)
Hays, Samuel P. Conservation and the Gospel of Efficiency: The Progressive Conservation Movement, 1890-1920. University of Pittsburgh Press, 1999.
Varning: dessa hänvisningar är inte alltid fullständigt riktiga.