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