Perhaps you should try some spelling variations:
voi nang » voi hang, hoi nang, voi rang
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
va nang » van nang, da nang, cam nang
hieu ve » hieu va, hieu van
cam duc » cam xuc, cao duc, pham duc
duc van » duc va, duc tan, duc manh
ve cam » ve cham, ve cac, va cam
x hoi » xa hoi, o hoi, x ho
vi su » ve su, ki su, oi 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 ((voi nang) or (va nang)) x hoi. hieu ve cam duc van hanh ((vi su) OR (va su)) triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ((voi nang) OR (va nang)) x hoi. hieu ve cam duc van hanh ((vi su) OR (va su)) triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ((voi nang) or (va nang)) x hoi. hieu ve cam duc van hanh ((vi su) OR (va su)) triet*".