Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
dang xay » dang van, van xay
cham luc » cham soc, nhan luc, cham cuu
cua tre » cua te, cuu tre, cua triet
va cham » va chat, va tham
tai cua » thai cua, tai cuc, tri cua
va hanh » va thanh, va danh, ban hanh
hieu va » lieu va, hieu qua
lang xa » lang ha, lang van
sai ky » sac ky
te sai » te tai, te bai, te lai

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

• Performing a fuzzy search may retrieve terms with similar spellings: te sai ky ((lang xa) OR (dang xay)) hoi. hieu va cham luc ((va hanh) or (van hanh)) tai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sai ky ((lang xa) OR (dang xay)) hoi. hieu va cham luc ((va hanh) OR (van hanh)) tai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sai ky ((lang xa) OR (dang xay)) hoi. hieu va cham luc ((va hanh) or (van hanh)) tai cua tre".
• Adding a wildcard symbol may retrieve word variants: te sai ky ((lang xa) OR (dang xay)) hoi. hieu va cham luc ((va hanh) or (van hanh)) tai cua tre*.