Perhaps you should try some spelling variations:
hanh tai » thanh tai, hang tai, han tai
van hanh » van thanh, ban hanh, van anh
lang xa » lang ha, dang xay, lang van
tai cua » thai cua, tai cuc, tri cua
nang xa » nang x, nang ma, mang xa
hoc van » hoc dan, hoc va, hoc vat
cac hoc » cach hoc, cac hop, bac hoc
qua cac » cua cac
sac ky » cac 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 ((sac ky) or (sai ky)) ((nang xa) or (lang xa)) hoi. hieu qua cac hoc van hanh tai cua cu~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te ((sac ky) OR (sai ky)) ((nang xa) OR (lang xa)) hoi. hieu qua cac hoc van hanh tai cua cu.
• Adding a wildcard symbol may retrieve word variants: te ((sac ky) or (sai ky)) ((nang xa) or (lang xa)) hoi. hieu qua cac hoc van hanh tai cua cu*.