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 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 » lieu va, hieu qua
vai va » mai va, dai va, hai va
va am » va lam, va cam

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

• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky ((nang co) OR (nang doc)) hoi. hieu va am ((thuc va) OR (thuc vat)) 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 am ((thuc va) OR (thuc vat)) dan vai va triet~".
• Adding a wildcard symbol may retrieve word variants: tu sach ky ((nang co) or (nang doc)) hoi. hieu va am ((thuc va) OR (thuc vat)) dan vai va triet*.