Perhaps you should try some spelling variations:
hieu viec » nhieu viec, sieu viet, hieu hien
sach nuoc » sach duoc, cac nuoc, bach tuoc
danh doi » thanh doi, dung doi, danh hoa
so sach » so sanh, bo sach, co sach
sach ky » sac ky, sach y, sach ty
danh di » danh du, xanh di, danh dien
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
nang o » nang co, nang ho, nang ro
o hai » co hai, so hai, o lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach ky nang o hai. ((hieu viec) or (hieu ve)) sach nuoc va ((danh doi) OR (danh di)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach ky nang o hai. ((hieu viec) OR (hieu ve)) sach nuoc va ((danh doi) OR (danh di)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach ky nang o hai. ((hieu viec) or (hieu ve)) sach nuoc va ((danh doi) OR (danh di)) cua tre".
• Adding a wildcard symbol may retrieve word variants: so sach ky nang o hai. ((hieu viec) or (hieu ve)) sach nuoc va ((danh doi) OR (danh di)) cua tre*.