Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
hoc viet » hoc hien
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 » va thanh, va danh, ban hanh
tai hoc » thai hoc, dai hoc, bai hoc
so sai » so dai, so hai, do sai
sai ky » sac 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 sai ky ((nang xa) or (lang xa)) hoi. hieu van dam tu ((va hanh) OR (van hanh)) tai hoc viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sai ky ((nang xa) OR (lang xa)) hoi. hieu van dam tu ((va hanh) OR (van hanh)) tai hoc viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sai ky ((nang xa) or (lang xa)) hoi. hieu van dam tu ((va hanh) OR (van hanh)) tai hoc viet".
• Adding a wildcard symbol may retrieve word variants: so sai ky ((nang xa) or (lang xa)) hoi. hieu van dam tu ((va hanh) OR (van hanh)) tai hoc viet*.