Perhaps you should try some spelling variations:
dieu hien » dieu khien, dieu kien, bieu hien
hien cac » thien cac, vien cac, hieu cac
van dinh » van minh, van dich, xuan dinh
vai cua » dai cua, hai cua, lai cua
va dinh » va kinh, va tinh, vu dinh
cac lao » ca lao, cac loai, cac giao
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
nang ma » tang ma, sang ma, nang cao
nang xa » nang x, lang xa, mang xa
cua tre » cua te, cuu tre, cua triet

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