Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
viec cac » vien cac, viec cua, viec lam
cao hoat » cac hoat, co hoat, cao chat
va lang » va nang, hoa lang
va hang » van hang, va nang, va hanh
tu sach » thu sach, su sach, te sach
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, may nang
cac tu » cac thu, cach tu, cac du
v nang » va nang, vu nang, van nang
va cua » va chua, via cua, ca cua

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ((y nang) or (v nang)) cao hoat. hieu viec cac tu ((va hang) OR (va lang)) va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((y nang) OR (v nang)) cao hoat. hieu viec cac tu ((va hang) OR (va lang)) va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((y nang) or (v nang)) cao hoat. hieu viec cac tu ((va hang) OR (va lang)) va cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ((y nang) or (v nang)) cao hoat. hieu viec cac tu ((va hang) OR (va lang)) va cua tre*.