Dyfyniad APA

(1994). Field Guide To The Birds Of North America. National Geographic society.

Dyfyniad Arddull Chicago

Field Guide To The Birds Of North America. National Geographic society, 1994.

Dyfyniad MLA

Field Guide To The Birds Of North America. National Geographic society, 1994.

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