Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
doanh cao » doanh co, doanh bao, doanh cho
va doanh » van doanh, vay doanh, va danh
cac nuoc » cap nuoc, dat nuoc, cua nuoc
cao cua » ca cua, co cua, cau cua
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
van hoe » van hoa, van hoc, van hieu
van hoi » van hoa, van hoc, van loi
ky lang » ky nang, ky dang, ky tang
cua tre » cua te, cuu tre, cua triet

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 ky lang ((van hoi) or (van hoe)). hieu viec ((cac nuoc) OR (hoc nuoc)) va doanh cao cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky lang ((van hoi) OR (van hoe)). hieu viec ((cac nuoc) OR (hoc nuoc)) va doanh cao cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky lang ((van hoi) or (van hoe)). hieu viec ((cac nuoc) OR (hoc nuoc)) va doanh cao cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky lang ((van hoi) or (van hoe)). hieu viec ((cac nuoc) OR (hoc nuoc)) va doanh cao cua tre*.