| The Origin of Man and of His Superstitions
Carveth Read | |
| The Origin of Metallic Currency and Weight Standards
William Ridgeway | |
| The Origin of Paul's Religion
J. Gresham Machen | |
| The Origin of Property in Land / With an introductory chapter on the English manor by W. J. Ashley
Fustel de Coulanges | |
| The Origin of Species / From 'The Westminster Review', April 1860
Thomas Henry Huxley | |
| The Origin of Species by Means of Natural Selection / Or, the Preservation of Favoured Races in the Struggle for Life, 6th Edition
Charles Darwin | |
| The origin of the family, private property, and the state
Friedrich Engels | |
| The Origin of the Knowledge of Right and Wrong
Franz Brentano | |
| The Origin of the Mound Builders
Alfred Oscar Coffin | |
| The Origin of the Red Cross: "Un souvenir de Solferino"
Henry Dunant |
