Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
cac cong » cua cong
van hanh » van thanh, ban hanh, van anh
te sach » toc sach
sach ty » sach y, sach tu, sach thu
ty nang » ky nang, ty xang, ty hang
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
vi cua » vai cua, di cua
o hoc » co hoc, mo hoc, so hoc

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 ty nang o hoc. hieu van ((cac co) OR (cac cong)) van hanh vi cua tre~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sach ty nang o hoc. hieu van ((cac co) OR (cac cong)) van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: te sach ty nang o hoc. hieu van ((cac co) OR (cac cong)) van hanh vi cua tre*.