Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van ban
nang doc » nang luc
van anh » van thanh, tuan anh, van minh
van cac » van hac, van cau, van bac
sach ty » sach y, sach tu, sach thu
te sach » toc sach
nang co » nang cao, nang noi, nang hoc
cua tre » cua te, cuu tre, cua triet
cac so » cac co, cac bo, cac ho
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ty ((nang co) or (nang doc)) hai. hieu van cac so ((van hanh) OR (van anh)) vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ty ((nang co) OR (nang doc)) hai. hieu van cac so ((van hanh) OR (van anh)) vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty ((nang co) or (nang doc)) hai. hieu van cac so ((van hanh) OR (van anh)) vi cua tre".
• Adding a wildcard symbol may retrieve word variants: te sach ty ((nang co) or (nang doc)) hai. hieu van cac so ((van hanh) OR (van anh)) vi cua tre*.