Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
cau treo » cau theo, cau triet, cau trieu
dang hai » dang khai, hang hai, dung hai
lanh hai » manh hai, thanh hai, lang chai
thuc va » thuc vat, thuc dan, thuc day
nang ma » tang ma, sang ma, nang cao
so sach » so sanh, bo sach, co sach
van am » van nam, van lam, van dam
y nang » ky nang, ly nang, v nang
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: so sach y nang ma hoi. hieu van am thuc va ((lanh hai) or (dang hai)) ((cau treo) OR (cau tren))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach y nang ma hoi. hieu van am thuc va ((lanh hai) OR (dang hai)) ((cau treo) OR (cau tren)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach y nang ma hoi. hieu van am thuc va ((lanh hai) or (dang hai)) ((cau treo) OR (cau tren))".
• Adding a wildcard symbol may retrieve word variants: so sach y nang ma hoi. hieu van am thuc va ((lanh hai) or (dang hai)) ((cau treo) OR (cau tren))*.