Cita APA (7th ed.)

Hagen, O. A. (2010). Digital books: Competition and commerce. Nova Science Publishers.

Cita Chicago (17th ed.)

Hagen, Oliver A. Digital Books: Competition and Commerce. New York: Nova Science Publishers, 2010.

Cita MLA (9th ed.)

Hagen, Oliver A. Digital Books: Competition and Commerce. Nova Science Publishers, 2010.