Enriques, Federigo Logic
Book by Louis Couturat, Benedetto Croce, Federigo Enriques, Nicolaj Losskij, B. Ethel Meyer, Josiah Royce, Arnold Ruge, Wilhelm Windelband; Macmillan, 1913
Enriques, Federigo Problems of Science
Book by Federigo Enriques, Katharine Royce; Open Court Publishing Company, 1914
Ensor, R. Belgium
Book by R. C. K. Ensor; H. Holt and Company, 1915