Perhaps you should try some spelling variations:
cao hoc » co hoc, cho hoc, chat hoc
hieu ve » hieu va, hieu van
duc van » duc tan, duc manh, duc phan
hanh di » hanh vi, hanh de, hang di
cuu tre » cua tre, cau tren, cau treo
sac ky » cac ky
ve bao » te bao, va bao
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 ((sac ky) or (sai ky)) nang cao hoc. hieu ve bao ((duc van) OR (duc va)) hanh di cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sac ky) OR (sai ky)) nang cao hoc. hieu ve bao ((duc van) OR (duc va)) hanh di cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sac ky) or (sai ky)) nang cao hoc. hieu ve bao ((duc van) OR (duc va)) hanh di cuu tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sac ky) or (sai ky)) nang cao hoc. hieu ve bao ((duc van) OR (duc va)) hanh di cuu tre*.