Perhaps you should try some spelling variations:
tan thanh » tran thanh, tang thanh, toan thanh
thanh hoi » thanh hoai, thanh hoa, thanh hai
sach thu » sach thue, sach thieu, sach tham
hieu van » hieu va, thien van, lieu va
xach tay » canh tay
hoi cua » hoi chuc
nam duc » nam duoc, pham duc, nam thuc
sang ma » tang ma, sang tao, mang may
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, nang cao, mang may

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

• Performing a fuzzy search may retrieve terms with similar spellings: so ((xach tay) or (sach thu)) ((nang ma) OR (sang ma)) hoi. hieu van nam duc tan thanh hoi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((xach tay) OR (sach thu)) ((nang ma) OR (sang ma)) hoi. hieu van nam duc tan thanh hoi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((xach tay) or (sach thu)) ((nang ma) OR (sang ma)) hoi. hieu van nam duc tan thanh hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: so ((xach tay) or (sach thu)) ((nang ma) OR (sang ma)) hoi. hieu van nam duc tan thanh hoi cua tre*.