Perhaps you should try some spelling variations:
va triet » va thiet, va trien, ve triet
nang doc » nang luc
dan vai » dan va, dan tai, dan vat
thuc va » thuc vat, thuc dan, thuc day
sach ky » sac ky, sach y, sach ty
tu sach » thu sach, su sach, te sach
nang co » nang cao, nang noi, nang hoc
hieu va » hieu qua
va dan » ca dan, va dao, va dau
vai va » mai va, dai va, hai va

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 ky ((nang co) or (nang doc)) hoi. ((hieu va) OR (lieu va)) am thuc va dan vai va triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang co) OR (nang doc)) hoi. ((hieu va) OR (lieu va)) am thuc va dan vai va triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky ((nang co) or (nang doc)) hoi. ((hieu va) OR (lieu va)) am thuc va dan vai va triet*".