Perhaps you should try some spelling variations:
te sach » toc sach
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
hanh va » hang va, hanh vi
su viet » so viet
va dam » van dam, va dao, va dau
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: ((te sach) or (hoc sinh)) ky ((nang xa) OR (nang ma)) hoi. hieu va dam tu va hanh va su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((te sach) OR (hoc sinh)) ky ((nang xa) OR (nang ma)) hoi. hieu va dam tu va hanh va su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((te sach) or (hoc sinh)) ky ((nang xa) OR (nang ma)) hoi. hieu va dam tu va hanh va su viet".
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (hoc sinh)) ky ((nang xa) OR (nang ma)) hoi. hieu va dam tu va hanh va su viet*.