Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » hieu va, thien van, lieu va
van cam » van nam, van lam, van cau
cua tre » cua te, cuu tre, cua triet
nang ma » tang ma, sang ma, nang cao
xac va » tac va, ac va, bac va
luc va » duc va, tuc va, loc va
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 ((nang x) or (nang ma)) hoi. hieu van cam ((xac va) or (luc va)) hanh vi 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 cam ((xac va) OR (luc va)) hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: thu sach y ((nang x) or (nang ma)) hoi. hieu van cam ((xac va) or (luc va)) hanh vi cua tre*.