Perhaps you should try some spelling variations:
hanh thai » nhanh thai, hinh thai, hanh tai
thai cua » than cua, tai cuc, tri cua
hieu ve » hieu va, hieu van
duc van » duc tan, duc manh, duc phan
cua tre » cua te, cuu tre, cua triet
dang xa » dang xay, lang xa, dang va
dang ha » dong ha, dung ha, lang ha
tai ky » thai ky, trai ky, sai ky
ve cac » va cac, vien cac
su tai » su thi, tu tai

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

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