Perhaps you should try some spelling variations:
kham thuc » nham thuc, pham thuc, tham thuc
cua viet » ca viet, hoa viet, cua vat
vai cua » dai cua, hai cua, lai cua
va dinh » van dinh, va kinh, va tinh
va danh » va dan, va hanh, dia danh
tu sach » thu sach, su sach, te sach
sach ha » sach nha, sach han, sach xa
hieu va » lieu va, hieu qua
nang xa » lang xa, nang ma, mang xa
va kham » va cham, va khao, va tham

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 ha ((nang xa) or (nang x)) hoi. hieu va kham thuc ((va danh) OR (va dinh)) vai cua viet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ha ((nang xa) OR (nang x)) hoi. hieu va kham thuc ((va danh) OR (va dinh)) vai cua viet.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ha ((nang xa) or (nang x)) hoi. hieu va kham thuc ((va danh) OR (va dinh)) vai cua viet".
• Adding a wildcard symbol may retrieve word variants: tu sach ha ((nang xa) or (nang x)) hoi. hieu va kham thuc ((va danh) OR (va dinh)) vai cua viet*.