Perhaps you should try some spelling variations:
hoc sach » hoc cac, hoc anh
nang co » nang cao, nang doc, nang noi
hieu ve » hieu van
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
hanh ca » hanh cac, hanh cat, hanh cua
cua tre » cua te, cuu tre, cua triet
thu va » thuc va, thue va, tu va
ca cua » co cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((hoc sach) OR (hoc sinh)) ky nang co hoc. ((hieu ve) or (hieu va)) nam thu va hanh ca cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((hoc sach) OR (hoc sinh)) ky nang co hoc. ((hieu ve) OR (hieu va)) nam thu va hanh ca cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((hoc sach) OR (hoc sinh)) ky nang co hoc. ((hieu ve) or (hieu va)) nam thu va hanh ca cua tre".
• Adding a wildcard symbol may retrieve word variants: ((hoc sach) OR (hoc sinh)) ky nang co hoc. ((hieu ve) or (hieu va)) nam thu va hanh ca cua tre*.