Perhaps you should try some spelling variations:
hieu van » hieu va, thien van, lieu va
nang xa » nang x, lang xa, nang ma
cac loc » cac lop, cac toc, cac nuoc
cac hoc » cach hoc, cac hop, bac hoc
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
can ky » van ky, ban ky, tan ky
dan ky » van 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: tu ((can ky) or (dan ky)) nang xa hoi. hieu van ((cac loc) OR (cac hoc)) va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((can ky) OR (dan ky)) nang xa hoi. hieu van ((cac loc) OR (cac hoc)) va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((can ky) or (dan ky)) nang xa hoi. hieu van ((cac loc) OR (cac hoc)) va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((can ky) or (dan ky)) nang xa hoi. hieu van ((cac loc) OR (cac hoc)) va hanh vi cua tre*.