Perhaps you should try some spelling variations:
vat hanh » vat thanh, van hanh, va hanh
hai thuc » thai thuc, dai thuc, ha thuc
su sach » so sach, vu sach
hieu va » lieu va, hieu qua
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, lang xa, mang xa
va hai » van hai, va chai, va khai
su xac » pu xac, su cac
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 (su xac)) ky ((nang xa) or (nang ma)) hoi. hieu va hai thuc vat hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((su sach) OR (su xac)) ky ((nang xa) OR (nang ma)) hoi. hieu va hai thuc vat hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: ((su sach) or (su xac)) ky ((nang xa) or (nang ma)) hoi. hieu va hai thuc vat hanh vi cua tre*.