Perhaps you should try some spelling variations:
thanh hoi » thanh hoai, thanh hoa, thanh hai
ban thanh » ban hanh, ban hang
sach ky » sach y, sach ty, sach kem
hoi cua » hoi chuc
dua ban » dia ban, cua ban, qua ban
cua tre » cua te, cuu tre, cua triet
ve cach » va cach, ve canh
ve cac » va cac, vien cac
sac ky » cac ky, sai ky
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 ((ve cach) OR (ve cac)) dua ban thanh hoi 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 ((ve cach) OR (ve cac)) dua ban thanh hoi 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 ((ve cach) OR (ve cac)) dua ban thanh hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) or (sac ky)) nang x hoi. hieu ((ve cach) OR (ve cac)) dua ban thanh hoi cua tre*.