Perhaps you should try some spelling variations:
nam duoc » nam thuoc, da duoc, dat duoc
hieu van » hieu va, thien van, lieu va
mang lai » mang lam, mang luoi, dang loai
nang lai » nang tai, nang cai, nang hai
sach ty » sach tu, sach thu, xach tay
duoc va » nuoc va, duc va, duoc ma
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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