Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
hieu van » thien van, lieu va, hieu ve
van doan » van doanh, van toan, van hoan
sach ky » sac ky, sach y, sach ty
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
va cua » va chua, via cua, ca cua
x hoi » xa hoi, o hoi, x ho

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 x hoi. ((hieu van) or (hieu va)) ((tac tu) or (cac du)) van doan va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky nang x hoi. ((hieu van) OR (hieu va)) ((tac tu) OR (cac du)) van doan va cua tre.
• Adding a wildcard symbol may retrieve word variants: thu sach ky nang x hoi. ((hieu van) or (hieu va)) ((tac tu) or (cac du)) van doan va cua tre*.