Perhaps you should try some spelling variations:
van hanh » van thanh, ban hanh, van anh
tu sach » thu sach, su sach, te sach
duc van » duc va, duc tan, duc manh
cau duc » cao duc, cau luc, chu duc
hieu ve » hieu va, hieu van
mai hoi » mai khoi, dai hoi, lai hoi
cua tre » cua te, cuu tre, cua triet
y nang » ky nang, ly nang, v nang
ma hoi » xa hoi, ma hoa, me hoi
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: tu sach y nang ((ma hoi) OR (mai hoi)). ((hieu ve) or (lieu va)) cau duc van hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach y nang ((ma hoi) OR (mai hoi)). ((hieu ve) OR (lieu va)) cau duc van hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach y nang ((ma hoi) OR (mai hoi)). ((hieu ve) or (lieu va)) cau duc van hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach y nang ((ma hoi) OR (mai hoi)). ((hieu ve) or (lieu va)) cau duc van hanh vi cua tre*.