Perhaps you should try some spelling variations:
nhanh thai » nhanh thi, nhanh thanh, nhanh thang
hanh thai » hinh thai, hanh tai, anh thai
cua tre » cua te, cuu tre, cua triet
dang xa » dang xay, lang xa, dang va
dang ha » dong ha, dung ha, lang ha
hieu ve » hieu va, hieu van
cac duc » cac du, cao duc, cac dac
duc van » duc va, duc tan, duc manh
su sai » su tai, su hai, su dai
sai ky » sac ky
ve cac » va cac, vien cac

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

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