Perhaps you should try some spelling variations:
chat thien » phat trien, cai thien, phat hien
thanh lam » thanh lap, hanh lam, thanh nam
van thanh » ban thanh, van tuan
lam chat » luan chat, cao chat, ly chat
hieu van » hieu va, thien van, lieu va
duc van » duc va, duc tan, duc manh
cau duc » cao duc, cau luc, chu duc
van cau » van dau, van hau, van chat
sach ky » sach y, sach ty, sach kem
sac ky » cac ky, sai ky
o hoi » co hoi, o hoc, o hoa
o hai » co hai, so hai, o lai

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 ((o hoi) or (o hai)). hieu van cau duc van thanh lam chat thien~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu ((sach ky) OR (sac ky)) nang ((o hoi) OR (o hai)). hieu van cau duc van thanh lam chat thien.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu ((sach ky) OR (sac ky)) nang ((o hoi) or (o hai)). hieu van cau duc van thanh lam chat thien".
• Adding a wildcard symbol may retrieve word variants: tu ((sach ky) OR (sac ky)) nang ((o hoi) or (o hai)). hieu van cau duc van thanh lam chat thien*.