Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
sach ky » sac ky, sach y, sach kem
va hanh » van hanh, va thanh, va danh
nam luc » nang luc, nhan luc, nam thuc
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet
nang xa » nang x, nang ma, mang xa
sach ty » sach y, sach tu, sach thu
luc va » duc va, tuc va, loc va
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: thu ((sach ky) or (sach ty)) ((nang xa) OR (lang xa)) hoi. hieu van nam luc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: thu ((sach ky) OR (sach ty)) ((nang xa) OR (lang xa)) hoi. hieu van nam luc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "thu ((sach ky) or (sach ty)) ((nang xa) OR (lang xa)) hoi. hieu van nam luc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: thu ((sach ky) or (sach ty)) ((nang xa) OR (lang xa)) hoi. hieu van nam luc va hanh vi cua tre*.