To claim preference under a certain trade agreement, traders must use exactly the form of certificate of origin devised for that agreement. Taking Vietnam as an example, a Vietnamese exporter will apply for a preferential certificate of origin Form A for GSP purposes, Form D if exported to another ASEAN country, Form E if exported to China under the ASEAN-China trade agreement, Form AK if exported to China under the ASEAN-Korea trade agreement, etc. Particularly, if his trade partner is a Japan importer, this Vietnamese exporter may need to choose among Form A (GSP), Form AJ (ASEAN-Japan) or Form VJ (Vietnam-Japan), depending on the preferential agreement that he opts to adhere to.