Perhaps you should try some spelling variations:
nang dau » hang dau, xang dau, nang du
nam truc » nam truoc, nam thuc, nam trung
ban hanh » ban hang
vinh cuu » dinh cuu, sinh cua, dinh cu
dau hoi » cau hoi, dai hoi, dan hoi
hieu va » lieu va, hieu qua
va hanh » van hanh, va thanh, va danh
tu sac » tu sach, tu cac, tu san
sac ky » cac ky, sai ky
va nam » van nam, ha nam, va nay
vi cuu » vi luu

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky nang dau hoi. hieu va nam truc ((va hanh) or (ban hanh)) ((vi cuu) or (vinh cuu)) tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky nang dau hoi. hieu va nam truc ((va hanh) OR (ban hanh)) ((vi cuu) OR (vinh cuu)) tre.
• Adding a wildcard symbol may retrieve word variants: tu sac ky nang dau hoi. hieu va nam truc ((va hanh) or (ban hanh)) ((vi cuu) or (vinh cuu)) tre*.