IODP SEDIS - Thesaurus -

Gulf of Tonkin
BT	Pacific Ocean
	.North Pacific
	..Northwest Pacific
	...South China Sea
	....Gulf of Tonkin
UF	Tonkin Gulf
RT	Hainan China
SN	Arm of the South China Sea, NE Vietnam. This term has multiple hierarchies. Added to Thesaurus in 1981.