Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
dinh vi » dinh ve, dinh viet, dinh tri
danh vi » hanh vi, danh di, danh va
nam mua » nam cua, nam qua, nam xua
cuu tre » cua tre, cau tren, cau treo
hieu va » lieu va, hieu qua
mua va » vua va, sua va, xua va
va nam » van nam, ha nam, va nay
o hoi » co hoi, o hoc, o hai
x hoi » xa hoi, x ho, 5 hoi

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 ((x hoi) OR (o hoi)). hieu va nam mua va ((danh vi) or (dinh vi)) cuu tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((x hoi) OR (o hoi)). hieu va nam mua va ((danh vi) OR (dinh vi)) cuu tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((x hoi) OR (o hoi)). hieu va nam mua va ((danh vi) or (dinh vi)) cuu tre".
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang ((x hoi) OR (o hoi)). hieu va nam mua va ((danh vi) or (dinh vi)) cuu tre*.