Perhaps you should try some spelling variations:
luoc can » luc canh, hoc can, luoc dai
cua tre » cua te, cuu tre, cua triet
duc van » duc va, duc tan, duc manh
hieu ve » hieu va, hieu van
tai hai » thi hai, dai hai, tai ha
tai hoi » tai khoi, dai hoi, tai hoe
ky hang » ky nang, ly hang, ky dang
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 hang ((tai hoi) OR (tai hai)). hieu ve cac ((duc van) or (luoc can)) hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: te sac ky hang ((tai hoi) OR (tai hai)). hieu ve cac ((duc van) OR (luoc can)) hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "te sac ky hang ((tai hoi) OR (tai hai)). hieu ve cac ((duc van) or (luoc can)) hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: te sac ky hang ((tai hoi) OR (tai hai)). hieu ve cac ((duc van) or (luoc can)) hanh vi cua tre*.