Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
nam thuc » nam thuoc, am thuc, nam thu
hieu van » hieu va, thien van, lieu va
sach ty » sach y, sach tu, sach thu
nang xa » nang x, lang xa, nang ma
nam tuc » nam truc, nam tu, nam thuoc
va hanh » van hanh, va thanh, va danh
sac ky » cac ky, sai ky
vi cua » vai cua, di cua

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

• Performing a fuzzy search may retrieve terms with similar spellings: su ((sac ky) or (sach ty)) nang xa hoi. hieu van ((nam tuc) OR (nam thuc)) va hanh vi cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su ((sac ky) OR (sach ty)) nang xa hoi. hieu van ((nam tuc) OR (nam thuc)) va hanh vi cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su ((sac ky) or (sach ty)) nang xa hoi. hieu van ((nam tuc) OR (nam thuc)) va hanh vi cua viet".
• Adding a wildcard symbol may retrieve word variants: su ((sac ky) or (sach ty)) nang xa hoi. hieu van ((nam tuc) OR (nam thuc)) va hanh vi cua viet*.