Perhaps you should try some spelling variations:
cau treo » cau theo, cau tren, cau triet
hieu van » hieu va, thien van, lieu va
dang hai » dang khai, hang hai, dung hai
danh hai » lanh hai, manh hai, danh hau
thuc dan » thuc hanh, hoc dan, thuc vat
su sach » so sach, vu sach
sach ly » sach y, sach lo, sach ty
nang ma » tang ma, sang ma, mang may
van am » van nam, van lam, van dam

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 ly ((nang ma) or (nang cao)) hoi. hieu van am thuc dan ((danh hai) OR (dang hai)) cau treo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ly ((nang ma) OR (nang cao)) hoi. hieu van am thuc dan ((danh hai) OR (dang hai)) cau treo.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ly ((nang ma) or (nang cao)) hoi. hieu van am thuc dan ((danh hai) OR (dang hai)) cau treo".
• Adding a wildcard symbol may retrieve word variants: su sach ly ((nang ma) or (nang cao)) hoi. hieu van am thuc dan ((danh hai) OR (dang hai)) cau treo*.