Perhaps you should try some spelling variations:
khanh thanh » nhanh thanh, thanh thanh, phan thanh
khanh thai » nhanh thai, khanh thuan, thanh hai
cau theo » cau thi, cau tao
hieu van » hieu va, thien van, lieu va
duc van » duc va, duc tan, duc manh
van cac » van hac, van cau, van bac
cac duc » cac du, cao duc, cac dac
sac ky » cac ky, sai ky
tu sac » tu sach, tu cac, tu san
o hai » co hai, so hai, o lai
o hoi » co hoi, o hoc, o hoa

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

• Performing a fuzzy search may retrieve terms with similar spellings: tu sac ky nang ((o hoi) or (o hai)). hieu van cac duc van ((khanh thai) or (khanh thanh)) cau theo~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sac ky nang ((o hoi) OR (o hai)). hieu van cac duc van ((khanh thai) OR (khanh thanh)) cau theo.
• Adding a wildcard symbol may retrieve word variants: tu sac ky nang ((o hoi) or (o hai)). hieu van cac duc van ((khanh thai) or (khanh thanh)) cau theo*.