Perhaps you should try some spelling variations:
khai truc » khai thac, dai truc, hai trac
su sach » so sach
va hanh » van hanh, va thanh, va danh
truc va » thuc va, thuc vat, trung va
va khai » van khai, va khao, va kha
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
mang xa » lang xa, mang may, dang xay
vu sach » vu bach, vu khach
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua

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) OR (vu sach)) ky ((mang xa) or (nang ma)) hoi. hieu va khai truc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (vu sach)) ky ((mang xa) OR (nang ma)) hoi. hieu va khai truc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((su sach) OR (vu sach)) ky ((mang xa) or (nang ma)) hoi. hieu va khai truc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: ((su sach) OR (vu sach)) ky ((mang xa) or (nang ma)) hoi. hieu va khai truc va hanh vi cua tre*.