Gaya APA

Nasional Geographic. (2015). : .

Gaya Chicago

Nasional Geographic. cet.1. : , 2015. Buku Teks.

Gaya MLA

Nasional Geographic. cet.1. : , 2015. Buku Teks.

Gaya Turabian

Nasional Geographic. : , 2015. Buku Teks.