APA

Asimov I. 1., .Fundation's edge: the fourth novel in foundation series. New York: Nightfal Inc.

Chicago

Asimov Isaac 1920-1992, .Fundation's edge: the fourth novel in foundation series. New York: Nightfal Inc.

Harvard

Asimov I. 1., .Fundation's edge: the fourth novel in foundation series. New York: Nightfal Inc.

MLA

Asimov Isaac 1920-1992, .New York: Nightfal Inc. .