Perhaps you should try some spelling variations:
cua tre » cua te, cuu tre, cua triet
hanh di » hanh vi, hanh de, hang di
hieu ve » hieu va, hieu van
ky sang » ky nang, ky dang, ky tang
sai ky » sac ky
ve cac » va cac, vien cac
ma hoi » mai hoi, xa hoi, me hoi
di cua » dai cua, doi cua, de cua
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 sang ((ma hoi) OR (ma hoa)). hieu ve cac ((duc tan) or (hoc dan)) hanh di cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sai ky sang ((ma hoi) OR (ma hoa)). hieu ve cac ((duc tan) OR (hoc dan)) hanh di cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sai ky sang ((ma hoi) OR (ma hoa)). hieu ve cac ((duc tan) or (hoc dan)) hanh di cua tre".
• Adding a wildcard symbol may retrieve word variants: te sai ky sang ((ma hoi) OR (ma hoa)). hieu ve cac ((duc tan) or (hoc dan)) hanh di cua tre*.