Perhaps you should try some spelling variations:
duoc tren » nuoc tren, thuoc tren, dung tren
hang tai » hang va, dung tai
duc tien » duc thien, luc tieng, thuc tien
vu sach » vu bach, su sach, vu khach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
ve pham » vi pham, v pham, ve phan
va hang » van hang, va nang, va lang
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 ty nang ma hoi. hieu ve pham duc va hang tai ((duc tien) or (duoc tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: vu sach ty nang ma hoi. hieu ve pham duc va hang tai ((duc tien) OR (duoc tren)).
• Adding a wildcard symbol may retrieve word variants: vu sach ty nang ma hoi. hieu ve pham duc va hang tai ((duc tien) or (duoc tren))*.