Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » thien van, lieu va, hieu ve
hai cau » hai chau, hai chu, hai hau
dan hai » doan hai, dang hai, dan khai
cau tuc » cau truc, cau tu, cau luc
hieu va » lieu va, hieu qua
su sach » vu sach
nang ma » tang ma, sang ma, nang cao
so sach » so sanh, bo sach, co sach
ma hoi » mai hoi, xa hoi, ma hoa
y nang » ky nang, ly nang, v nang
tuc va » thuc va, truc va, tuc xa
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 ma hoi. ((hieu van) OR (hieu va)) cau tuc va dan hai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (so sach)) y nang ma hoi. ((hieu van) OR (hieu va)) cau tuc va dan hai cau tren*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) or (so sach)) y nang ma hoi. ((hieu van) OR (hieu va)) cau tuc va dan hai cau tren*".