Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
van hanh » van thanh, ban hanh, van anh
te sach » toc sach
sach ky » sac ky, sach y, sach ty
nang xa » nang x, nang ma, mang xa
lang xa » lang ha, dang xay, lang van
cua tre » cua te, cuu tre, cua triet
vi cua » vai cua, di cua
hac o » hoc o, cac o, hap o

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: te sach ky ((nang xa) or (lang xa)) hoi. hieu van ((hac o) OR (sac o)) van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sach ky ((nang xa) OR (lang xa)) hoi. hieu van ((hac o) OR (sac o)) van hanh vi cua tre*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ky ((nang xa) or (lang xa)) hoi. hieu van ((hac o) OR (sac o)) van hanh vi cua tre*".