Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
hanh dai » hanh tai, hanh dao, vanh dai
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
qua cac » cua cac
cac hoc » cach hoc, cac hop, bac hoc
hoc van » hoc dan, hoc va, hoc vat
sai ky » sac ky
cua cu » cua chu, cua cau, cua su

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

• Performing a fuzzy search may retrieve terms with similar spellings: te ((cac ky) or (sai ky)) ((nang xa) or (lang xa)) hoi. hieu qua cac hoc van hanh dai cua cu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((cac ky) OR (sai ky)) ((nang xa) OR (lang xa)) hoi. hieu qua cac hoc van hanh dai cua cu.
• Adding a wildcard symbol may retrieve word variants: te ((cac ky) or (sai ky)) ((nang xa) or (lang xa)) hoi. hieu qua cac hoc van hanh dai cua cu*.