Perhaps you should try some spelling variations:
tinh viet » trinh viet, ninh viet, dinh viet
viet cua » viec cua, viet ca, viet qua
te sach » toc sach
sach ty » sach y, sach tu, sach thu
hieu ve » hieu va, hieu van
nang ma » tang ma, nang cao, mang may
sang ma » tang ma, sang tao, mang may
cua tre » cua te, cuu tre, cua triet
ve cac » va cac, vien cac
dac va » day va, dat va, dai 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 ty ((sang ma) or (nang ma)) hoi. hieu ve cac ((dac va) OR (duc va)) tinh viet cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((sang ma) OR (nang ma)) hoi. hieu ve cac ((dac va) OR (duc va)) tinh viet cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((sang ma) or (nang ma)) hoi. hieu ve cac ((dac va) OR (duc va)) tinh viet cua tre*".