Perhaps you should try some spelling variations:
van thanh » ban thanh, van tuan
thanh hoi » thanh hoai, thanh hoa, thanh hai
hieu van » hieu va, thien van, lieu va
nam thuc » nam thuoc, am thuc, nam tu
sach ty » sach y, sach thu, xach tay
sach tu » sach thu, cach tu, sach uu
nang xa » nang x, lang xa, nang ma
hoi cua » hoi chuc
cua tre » cua te, cuu tre, cua triet

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: so ((sach ty) or (sach tu)) nang xa hoi. hieu van ((nam thuc) OR (nam thu)) van thanh hoi cua tre~.
• If you are trying to use Boolean operators, they must be ALL CAPS: so ((sach ty) OR (sach tu)) nang xa hoi. hieu van ((nam thuc) OR (nam thu)) van thanh hoi cua tre.
• The words AND, OR and NOT may confuse the search; try adding quotes: "so ((sach ty) or (sach tu)) nang xa hoi. hieu van ((nam thuc) OR (nam thu)) van thanh hoi cua tre".
• Adding a wildcard symbol may retrieve word variants: so ((sach ty) or (sach tu)) nang xa hoi. hieu van ((nam thuc) OR (nam thu)) van thanh hoi cua tre*.