Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
nang doc » nang luc
cua tre » cua te, cua triet, dua tren
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
cuu tre » cau tren, cau treo
cac so » cac co, cac bo, cac ho
so van » su van, vo van

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 vi ((cua tre) OR (cuu 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 vi ((cua tre) OR (cuu 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 vi ((cua tre) OR (cuu tre))".
• Adding a wildcard symbol may retrieve word variants: te sach ty ((nang co) or (nang doc)) hai. hieu van cac so van hanh vi ((cua tre) OR (cuu tre))*.