Perhaps you should try some spelling variations:
tu sach » thu sach, te sach, tu cach
hieu ve » hieu va, hieu van
cuu tre » cua tre, cau tren, cau treo
su sach » so sach, vu sach
nang o » nang co, nang ho, nang ro
cac su » cach su, cac sau, cac du
dao ve » bao ve, dap ve, dau ve
dao va » dao van, tao va, do va
ve cac » va cac, vien cac
o hoi » co hoi, o hoc, o hai
su va » su van, tu va

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