Perhaps you should try some spelling variations:
tu sach » thu sach, su sach, te sach
sach ky » sac ky, sach y, sach ty
qua hai » qua hoat
dua ban » dia ban, cua ban, qua ban
cua tre » cua te, cuu tre, cua triet
nang o » nang co, nang ho, nang ro
anh do » anh doc, anh d, anh co
do cua » doi cua, co cua, de cua
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 qua hai ((duc tan) or (dua ban)) anh do cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang o hoi. hieu qua hai ((duc tan) OR (dua ban)) anh do cua tre*.