APA

Höffding H., . (1906). The problems of philosophy. New York: MacMillan.

Chicago

Höffding Harald, . 1906. The problems of philosophy. New York: MacMillan.

Harvard

Höffding H., . (1906). The problems of philosophy. New York: MacMillan.

MLA

Höffding Harald, . The problems of philosophy. New York: MacMillan. 1906.