Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
sach ky » sac ky, sach y, sach ty
hanh di » hanh vi, hanh de, hang di
duc van » duc va, duc tan, duc manh
cuu tre » cua tre, cau tren, cau treo
cao hoc » co hoc, cho hoc, chat hoc
ve dao » de dao, va dao, te dao
ve bao » te bao, va bao
sai ky » sac ky
di cuu » di cau, di cua, dinh cuu

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) or (sai ky)) nang cao hoc. hieu ((ve dao) OR (ve bao)) duc van hanh di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sai ky)) nang cao hoc. hieu ((ve dao) OR (ve bao)) duc van hanh di cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (sai ky)) nang cao hoc. hieu ((ve dao) OR (ve bao)) duc van hanh di cuu tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sai ky)) nang cao hoc. hieu ((ve dao) OR (ve bao)) duc van hanh di cuu tre*.