Perhaps you should try some spelling variations:
duoc tren » nuoc tren, thuoc tren, dung tren
hang tai » hang va, dung tai
duc tre » duc tien
va hang » van hang, va nang, va lang
vu sach » vu bach, su sach, vu khach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
ma hoi » mai hoi, xa hoi, ma hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: vu sach ky nang ma hoi. ((hieu ve) OR (hieu va)) pham duc va hang tai ((duc tre) or (duoc tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ky nang ma hoi. ((hieu ve) OR (hieu va)) pham duc va hang tai ((duc tre) OR (duoc tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "vu sach ky nang ma hoi. ((hieu ve) OR (hieu va)) pham duc va hang tai ((duc tre) or (duoc tren))".
• Adding a wildcard symbol may retrieve word variants: vu sach ky nang ma hoi. ((hieu ve) OR (hieu va)) pham duc va hang tai ((duc tre) or (duoc tren))*.