Perhaps you should try some spelling variations:
dau tren » dau tien, dat tren, dau tieng
danh hai » dang hai, lanh hai, manh hai
hieu van » hieu va, thien van, lieu va
hai dau » han dau, hai dan, hai hau
nang ma » tang ma, sang ma, nang cao
sach ty » sach tu, sach thu, xach tay
van cam » van nam, van lam, van cau
ma hoi » mai hoi, xa hoi, ma hoa
tuc va » thuc va, truc va, tuc xa

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 y) or (sach ty)) nang ma hoi. hieu van cam ((tuc va) or (thuc vat)) danh hai dau tren~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sach y) OR (sach ty)) nang ma hoi. hieu van cam ((tuc va) OR (thuc vat)) danh hai dau tren.
• Adding a wildcard symbol may retrieve word variants: su ((sach y) or (sach ty)) nang ma hoi. hieu van cam ((tuc va) or (thuc vat)) danh hai dau tren*.