Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
hanh tai » thanh tai, hang tai, han tai
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
van dam » van nam, van dao, van dau
va hanh » van hanh, va thanh, va danh
tai hoc » thai hoc, dai hoc, bai hoc
so sac » so sach, so dac
sac ky » cac ky, sai ky
dam tu » nam tu, cam tu, tam tu

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sac ky ((nang xa) or (lang xa)) hoi. hieu van dam tu va hanh tai hoc (hien OR bien)~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sac ky ((nang xa) OR (lang xa)) hoi. hieu van dam tu va hanh tai hoc (hien OR bien).
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sac ky ((nang xa) or (lang xa)) hoi. hieu van dam tu va hanh tai hoc (hien OR bien)".
• Adding a wildcard symbol may retrieve word variants: so sac ky ((nang xa) or (lang xa)) hoi. hieu van dam tu va hanh tai hoc (hien OR bien)*.