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
su viet » so viet
va nam » van nam, ha nam, va nay
nam tu » nam thu, nam thuc
vi su » va su, ve su, ki 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 sach) or (hoc sinh)) ky ((nang xa) or (nang ma)) hoi. hieu va nam tu va hanh vi 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 nam tu va hanh vi su viet.
• Adding a wildcard symbol may retrieve word variants: ((te sach) or (hoc sinh)) ky ((nang xa) or (nang ma)) hoi. hieu va nam tu va hanh vi su viet*.