Perhaps you should try some spelling variations:
hanh thai » nhanh thai, hinh thai, hanh tai
duc manh » suc manh, duc anh, duc minh
thai cua » than cua, tai cuc, tri cua
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
hieu ve » hieu van
hieu va » lieu va, hieu qua
duc van » duc va, duc tan, duc phan
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
o hai » co hai, so hai, o lai

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 ky nang o hai. ((hieu ve) or (hieu va)) cac ((duc van) OR (duc manh)) hanh thai cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o hai. ((hieu ve) OR (hieu va)) cac ((duc van) OR (duc manh)) hanh thai cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang o hai. ((hieu ve) or (hieu va)) cac ((duc van) OR (duc manh)) hanh thai cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hai. ((hieu ve) or (hieu va)) cac ((duc van) OR (duc manh)) hanh thai cua tre*.