Perhaps you should try some spelling variations:
thu sach » tu sach, thuat sach, thuoc sach
duc toan » duc tan, duc ton, duc hoan
cao duc » dao duc, cao suc, giao duc
cua tre » cua te, cuu tre, cua triet
hieu ve » hieu va, hieu van
tang xa » trang xa, tang ma, lang xa
ky tang » ky nang, ky dang, kho tang
anh vi » anh va, anh ve, anh vu
ve cao » va cao, ve bao, ve cac

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

• Performing a fuzzy search may retrieve terms with similar spellings: ((thu sach) or (thu hoach)) ky tang xa hoi. hieu ve cao duc toan ((anh vi) OR (hanh vi)) cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: ((thu sach) OR (thu hoach)) ky tang xa hoi. hieu ve cao duc toan ((anh vi) OR (hanh vi)) cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((thu sach) or (thu hoach)) ky tang xa hoi. hieu ve cao duc toan ((anh vi) OR (hanh vi)) cua tre".
• Adding a wildcard symbol may retrieve word variants: ((thu sach) or (thu hoach)) ky tang xa hoi. hieu ve cao duc toan ((anh vi) OR (hanh vi)) cua tre*.