Perhaps you should try some spelling variations:
hoang van » hang va
dang xay » dang van, van xay
va hanh » van hanh, va thanh, va danh
cac loc » cac lop, cac toc, cac hoc
hieu va » hieu qua
cua tre » cua te, cuu tre, cua triet
sai ky » sac ky
loc va » hoc va, luc va
vi cua » vai cua, di cua
tu sai » tu bai, tu san, tu cai

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sai ky ((dang xay) or (hoang van)) hoi. ((hieu va) or (lieu va)) cac loc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sai ky ((dang xay) OR (hoang van)) hoi. ((hieu va) OR (lieu va)) cac loc va hanh vi cua tre.
• Adding a wildcard symbol may retrieve word variants: tu sai ky ((dang xay) or (hoang van)) hoi. ((hieu va) or (lieu va)) cac loc va hanh vi cua tre*.