Perhaps you should try some spelling variations:
cua viet » ca viet, hoa viet, cua vat
van hanh » van thanh, ban hanh, van anh
nang tai » hang tai, tang tai, sang tai
va hanh » va thanh, va danh, ban hanh
sach va » sach xa, sach ha, sach dao
so sach » so sanh, bo sach, co sach
nang ma » tang ma, sang ma, nang cao
hieu ve » hieu va, hieu van
va cua » va chua, via cua, ca cua
ve am » va am

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

• Performing a fuzzy search may retrieve terms with similar spellings: so sach va ((nang ma) or (nang tai)) hoi. hieu ve am thuc ((va hanh) OR (van hanh)) va cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so sach va ((nang ma) OR (nang tai)) hoi. hieu ve am thuc ((va hanh) OR (van hanh)) va cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so sach va ((nang ma) or (nang tai)) hoi. hieu ve am thuc ((va hanh) OR (van hanh)) va cua viet".
• Adding a wildcard symbol may retrieve word variants: so sach va ((nang ma) or (nang tai)) hoi. hieu ve am thuc ((va hanh) OR (van hanh)) va cua viet*.