Perhaps you should try some spelling variations:
doan dau » doan dieu, phan dau, doan va
dau cua » dai cua, day cua, cau cua
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
te sach » toc sach
hieu so » thieu so
sang ma » tang ma, sang tao, mang may
nang ma » tang ma, nang cao, mang may
cua tre » cua te, cuu tre, cua triet
tuc va » truc va, tuc xa, duc va

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky ((nang ma) OR (sang ma)) hoi. hieu so kham ((tuc va) or (thuc va)) doan dau cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky ((nang ma) OR (sang ma)) hoi. hieu so kham ((tuc va) OR (thuc va)) doan dau cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((nang ma) OR (sang ma)) hoi. hieu so kham ((tuc va) or (thuc va)) doan dau cua tre".
• Adding a wildcard symbol may retrieve word variants: te sach ky ((nang ma) OR (sang ma)) hoi. hieu so kham ((tuc va) or (thuc va)) doan dau cua tre*.