Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
cuu tre » cau tren, cau treo
cua tre » cua te, cua triet, dua tren
nang o » nang co, nang ho, nang ro
ve cac » vien cac
va dao » ca dao
dao ve » bao ve, dap ve, dau ve
o hoi » co hoi, o hoc, o hai

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 hoi. hieu ((ve cac) or (va cac)) tu va dao ve ((cuu tre) or (cua tre))~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o hoi. hieu ((ve cac) OR (va cac)) tu va dao ve ((cuu tre) OR (cua tre)).
• Adding a wildcard symbol may retrieve word variants: tu sach ky nang o hoi. hieu ((ve cac) or (va cac)) tu va dao ve ((cuu tre) or (cua tre))*.