Perhaps you should try some spelling variations:
hieu van » thien van, lieu va, hieu ve
dua tren » dung tren
su sach » vu sach
so sach » so sanh, bo sach, co sach
cao hoi » cau hoi, co hoi, cao hoc
hieu va » lieu va, hieu qua
truc va » thuc va, thuc vat, trung va
dan hai » doan hai, dang hai, dan khai
hai dua » hai cua, dai dua, hai qua
y nang » ky nang, ly nang, v nang
va dan » ca dan, va dao, va dau

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((su sach) or (so sach)) y nang cao hoi. ((hieu van) OR (hieu va)) cau truc va dan hai dua tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) y nang cao hoi. ((hieu van) OR (hieu va)) cau truc va dan hai dua tren*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) y nang cao hoi. ((hieu van) OR (hieu va)) cau truc va dan hai dua tren*".