Perhaps you should try some spelling variations:
sang tao » hang tai
duc van » duc va, duc tan, duc manh
hieu ve » hieu va, hieu van
cua tre » cua te, cuu tre, cua triet
sang ma » tang ma, nang ma, mang may
sac ky » cac ky, sai ky
ve cac » va cac, vien cac
vi cua » vai cua, di cua
te sac » te sach, te cac, te san

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