Perhaps you should try some spelling variations:
cua tre » cua te, cuu tre, cua triet
hoc can » hoc dan, hoc cao, hoc cac
hieu ve » hieu va, hieu van
sang ma » tang ma, nang ma, sang tao
ma hoi » mai hoi, xa hoi, ma hoa
sac ky » cac ky
ve cac » va cac, vien cac
vi cua » vai cua, di cua

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

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