Perhaps you should try some spelling variations:
mai khoi » mai khoa, tai khoa, cac khoi
van hanh » van thanh, ban hanh, van anh
vuc nang » cuc nang, chuc nang, van nang
hanh ki » hanh vi, hanh ky, hanh kien
luc van » luoc van, luu van, duc van
cam luc » cam xuc, cau luc
hieu va » lieu va, hieu qua
tu sach » thu sach, su sach, te sach
mai hoi » dai hoi, lai hoi, mai doi
vu nang » va nang, vu dang, v nang
su viet » so viet
va cam » va cham, va cac, va cao
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) OR (vuc nang)) ((mai hoi) or (mai khoi)). hieu va cam luc van hanh ki su viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((vu nang) OR (vuc nang)) ((mai hoi) OR (mai khoi)). hieu va cam luc van hanh ki su viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((vu nang) OR (vuc nang)) ((mai hoi) or (mai khoi)). hieu va cam luc van hanh ki su viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ((vu nang) OR (vuc nang)) ((mai hoi) or (mai khoi)). hieu va cam luc van hanh ki su viet*.