APA

Heinlein R. A., . (1981). Time enough for love. New York: NEL.

Chicago

Heinlein Robert A, . 1981. Time enough for love. New York: NEL.

Harvard

Heinlein R. A., . (1981). Time enough for love. New York: NEL.

MLA

Heinlein Robert A, . Time enough for love. New York: NEL. 1981.