Perhaps you should try some spelling variations:
khach ky » hanh ky
thanh ky » hanh ky, than ky, thanh tay
cac nuoc » cap nuoc, hoc nuoc, dat nuoc
va nang » van nang, da nang, cam nang
va hang » van hang, va lang, va hanh
hieu va » lieu va, hieu qua
tang xa » trang xa, tang ma, lang xa
cua tre » cua te, cuu tre, cua triet
di cua » dai cua, doi cua, de cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: vu ((khach ky) or (thanh ky)) tang xa hoi. hieu va cac nuoc ((va hang) OR (va nang)) di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu ((khach ky) OR (thanh ky)) tang xa hoi. hieu va cac nuoc ((va hang) OR (va nang)) di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu ((khach ky) or (thanh ky)) tang xa hoi. hieu va cac nuoc ((va hang) OR (va nang)) di cua tre".
• Adding a wildcard symbol may retrieve word variants: vu ((khach ky) or (thanh ky)) tang xa hoi. hieu va cac nuoc ((va hang) OR (va nang)) di cua tre*.