Perhaps you should try some spelling variations:
cau tren » cu tren, dau tren, ca tren
hieu van » hieu va, thien van, lieu va
danh hai » dang hai, lanh hai, manh hai
thuc dan » thuc hanh, hoc dan, thuc vat
hai cau » hai chau, hai chu, hai hau
thuc va » thuc vat, thuc day
sach ly » sach y, sach lo, sach hay
sang ma » tang ma, nang ma, sang tao
sach ty » sach y, sach tu, sach thu
van cam » van nam, van lam, van cau
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: su ((sach ly) or (sach ty)) sang ma hoi. hieu van cam ((thuc va) or (thuc dan)) danh hai cau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach ly) OR (sach ty)) sang ma hoi. hieu van cam ((thuc va) OR (thuc dan)) danh hai cau tren.
• Adding a wildcard symbol may retrieve word variants: su ((sach ly) or (sach ty)) sang ma hoi. hieu van cam ((thuc va) or (thuc dan)) danh hai cau tren*.