Perhaps you should try some spelling variations:
thien van » thi van
hieu van » hieu va, lieu va, hieu ve
hai thuc » thai thuc, dai thuc, ha thuc
vat hanh » vat thanh, van hanh, va hanh
nang xa » nang x, lang xa, mang xa
nang ma » tang ma, sang ma, nang cao
cua tre » cua te, cuu tre, cua triet
su sac » su sach, su cac, su xac
sac ky » cac ky, sai ky
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 sac ky ((nang xa) or (nang ma)) hoi. ((hieu van) OR (thien van)) hai thuc vat hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: su sac ky ((nang xa) OR (nang ma)) hoi. ((hieu van) OR (thien van)) hai thuc vat hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "su sac ky ((nang xa) or (nang ma)) hoi. ((hieu van) OR (thien van)) hai thuc vat hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: su sac ky ((nang xa) or (nang ma)) hoi. ((hieu van) OR (thien van)) hai thuc vat hanh vi cua tre*.