Perhaps you should try some spelling variations:
cua triet » cua viet, su triet, va triet
dinh viet » ninh viet, danh viet, trinh viet
su sach » so sach, vu sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
hieu va » lieu va, hieu qua
va dinh » van dinh, va kinh, va tinh
cua tre » cua te, cuu tre, dua tren
du va » dau va, tu va, su va

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

• Performing a fuzzy search may retrieve terms with similar spellings: su sach ky ((nang x) or (nang ma)) hoi. hieu va cac du va dinh viet ((cua tre) OR (cua triet))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sach ky ((nang x) OR (nang ma)) hoi. hieu va cac du va dinh viet ((cua tre) OR (cua triet)).
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sach ky ((nang x) or (nang ma)) hoi. hieu va cac du va dinh viet ((cua tre) OR (cua triet))".
• Adding a wildcard symbol may retrieve word variants: su sach ky ((nang x) or (nang ma)) hoi. hieu va cac du va dinh viet ((cua tre) OR (cua triet))*.