Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
xuc van » duc van, luc van, vuc van
hieu va » lieu va, hieu qua
tu sach » thu sach, su sach, te sach
mai hoi » mai khoi, dai hoi, lai hoi
va nang » van nang, da nang, cam nang
vu nang » vuc nang, vu dang, v nang
va cam » va cham, va cac, va cao

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 (va nang)) mai hoi. hieu va cam xuc van hanh ((ki su) OR (ky su)) tien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((vu nang) OR (va nang)) mai hoi. hieu va cam xuc van hanh ((ki su) OR (ky su)) tien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((vu nang) or (va nang)) mai hoi. hieu va cam xuc van hanh ((ki su) OR (ky su)) tien".
• Adding a wildcard symbol may retrieve word variants: tu sach ((vu nang) or (va nang)) mai hoi. hieu va cam xuc van hanh ((ki su) OR (ky su)) tien*.