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