Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
ky dang » ky nang, ky danh
xay hoi » tay hoi, cay phoi, gay thoi
hieu va » hieu qua
cac loc » cac lop, cac toc, cac hoc
va hanh » van hanh, va thanh, va danh
cua tre » cua te, cuu tre, cua triet
loc va » hoc va, luc va
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 ky dang ((xay hoi) OR (xa hoi)). ((hieu va) or (lieu va)) cac loc va hanh vi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky dang ((xay hoi) OR (xa hoi)). ((hieu va) OR (lieu va)) cac loc va hanh vi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky dang ((xay hoi) OR (xa hoi)). ((hieu va) or (lieu va)) cac loc va hanh vi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky dang ((xay hoi) OR (xa hoi)). ((hieu va) or (lieu va)) cac loc va hanh vi cua tre*.