Perhaps you should try some spelling variations:
hieu vien » hieu hien, hieu viec, thieu nien
vien cac » vien bach, vien dai, vien da
van dinh » van minh, van dich, xuan dinh
tu sach » thu sach, su sach, te sach
vai cua » dai cua, hai cua, lai cua
va dinh » va kinh, va tinh, vu dinh
cua tre » cua te, cuu tre, cua triet
sach ky » sac ky, sach y, sach ty
nang xa » lang xa, nang ma, mang xa
cac lo » cac lop, cac co, cac bo

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