Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
doan vi » doan va, don vi, doan thi
va doan » va doanh, van doan, va dan
hieu va » lieu va, hieu qua
cua tre » cua te, cuu tre, cua triet
ty nang » ky nang, ty hang, ly nang
vi cua » vai cua, di 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 ((ty nang) or (ty xang)) x hoi. hieu va ((tac tu) or (cac du)) va doan vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ((ty nang) OR (ty xang)) x hoi. hieu va ((tac tu) OR (cac du)) va doan vi cua tre.
• Adding a wildcard symbol may retrieve word variants: thu sach ((ty nang) or (ty xang)) x hoi. hieu va ((tac tu) or (cac du)) va doan vi cua tre*.