Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
hanh tai » thanh tai, hang tai, han tai
tai cua » thai cua, tai cuc, tri cua
van lam » van nam
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
luc va » duc va, tuc va, loc va
ac va » tac va, bac va, mac va

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 x) or (nang ma)) hoi. hieu van lam ((ac va) or (luc va)) hanh tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach y ((nang x) OR (nang ma)) hoi. hieu van lam ((ac va) OR (luc va)) hanh tai cua tre.
• Adding a wildcard symbol may retrieve word variants: thu sach y ((nang x) or (nang ma)) hoi. hieu van lam ((ac va) or (luc va)) hanh tai cua tre*.