Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
truc van » truc va, thuc van, truc ban
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
sach vu » sach va, sach tu, sach uu
vu nang » vuc nang, va nang, vu dang
mai hoi » dai hoi, lai hoi, mai doi
hieu va » lieu va, hieu qua
hanh ki » hanh vi, hanh ky, hanh kien
su viet » so viet
va cau » van cau, va cac, va dau
ki su » ky su

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach vu nang ((mai hoi) or (mai khoi)). hieu va cau truc van hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach vu nang ((mai hoi) OR (mai khoi)). hieu va cau truc van hanh ki su viet.
• Adding a wildcard symbol may retrieve word variants: tu sach vu nang ((mai hoi) or (mai khoi)). hieu va cau truc van hanh ki su viet*.