Perhaps you should try some spelling variations:
duoc tuan » duoc luan, quoc tuan, duoc thanh
thu sach » tu sach, thuat sach, thuoc sach
nam duoc » nam thuoc, da duoc, dat duoc
hieu van » hieu va, thien van, lieu va
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
hanh va » hang va, hanh vi
cua tre » cua te, cuu tre, cua triet

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

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