APA

Heard G., . (1944). A preface to prayer. New York: Harper and brothers.

Chicago

Heard Gerald, . 1944. A preface to prayer. New York: Harper and brothers.

Harvard

Heard G., . (1944). A preface to prayer. New York: Harper and brothers.

MLA

Heard Gerald, . A preface to prayer. New York: Harper and brothers. 1944.