Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
ban hang » ngan hang
duoc ban » duc ban, quoc ban, buoc ban
lam duoc » nam duoc, luat duoc, lam thuoc
hieu van » thien van, lieu va, hieu ve
hieu va » lieu va, hieu qua
hang vi » hang va, hanh vi, hang di
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, mang may
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 ky ((nang ma) or (nang cao)) hoi. ((hieu van) OR (hieu va)) lam duoc ban hang vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky ((nang ma) OR (nang cao)) hoi. ((hieu van) OR (hieu va)) lam duoc ban hang vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky ((nang ma) or (nang cao)) hoi. ((hieu van) OR (hieu va)) lam duoc ban hang vi cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ky ((nang ma) or (nang cao)) hoi. ((hieu van) OR (hieu va)) lam duoc ban hang vi cua tre*.