Perhaps you should try some spelling variations:
hieu viec » nhieu viec, hieu ve, sieu viet
hieu vien » hieu hien, thieu nien, hieu tieng
thu sach » tu sach, thuat sach, thuoc sach
hanh va » hang va, hanh vi
va hanh » van hanh, va thanh, va danh
cac lop » cac hop, cac loai
cua tre » cua te, cuu tre, cua triet
nang xa » lang xa, nang ma, mang xa
sach ky » sac ky, sach y, sach ty
lop va » lap va, hop va, nop va
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: thu sach ky ((nang xa) or (nang x)) hoi. ((hieu vien) OR (hieu viec)) cac lop va hanh va cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu sach ky ((nang xa) OR (nang x)) hoi. ((hieu vien) OR (hieu viec)) cac lop va hanh va cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu sach ky ((nang xa) or (nang x)) hoi. ((hieu vien) OR (hieu viec)) cac lop va hanh va cua tre".
• Adding a wildcard symbol may retrieve word variants: thu sach ky ((nang xa) or (nang x)) hoi. ((hieu vien) OR (hieu viec)) cac lop va hanh va cua tre*.