Perhaps you should try some spelling variations:
qua cham » qua hai, qua cac, va cham
dua ban » dia ban, cua ban, qua ban
duc ban » duc tan, duc van, duc man
sach ky » sach y, sach ty, sach kem
cua tre » cua te, cuu tre, cua triet
anh do » anh doc, anh d, anh co
sac ky » cac ky, sai ky
do cua » doi cua, co cua, de cua
x hoi » xa hoi, o hoi, x ho

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) OR (sac ky)) nang x hoi. hieu qua cham ((duc ban) or (dua ban)) anh do cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang x hoi. hieu qua cham ((duc ban) OR (dua ban)) anh do cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sac ky)) nang x hoi. hieu qua cham ((duc ban) or (dua ban)) anh do cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sac ky)) nang x hoi. hieu qua cham ((duc ban) or (dua ban)) anh do cua tre*.