APA

Held (Gillbert), . (1999). Understanding Data Communications.Ed.6. : .

Chicago

Held (Gillbert), . 1999. Understanding Data Communications.Ed.6. : .

Harvard

Held (Gillbert), . (1999). Understanding Data Communications.Ed.6. : .

MLA

Held (Gillbert), . Understanding Data Communications.Ed.6. : . 1999.