Dyfyniad APA

National geographic. (2015). Known universe. National geographic.

Dyfyniad Arddull Chicago

National geographic. Known Universe. Washington, D.C: National geographic, 2015.

Dyfyniad MLA

National geographic. Known Universe. National geographic, 2015.

Rhybudd: Mae'n bosib nad yw'r dyfyniadau hyn bob amser yn 100% cywir.