Perhaps you should try some spelling variations:
canh trinh » canh tranh, hanh trinh, canh tinh
trinh quan » tinh quang, trinh luat, trinh han
hieu manh » chieu xanh, hieu nganh, dieu hanh
dung cong » dung trong
bang song » nang song
hoc hieu » hoc thieu, hoc hien, doc hieu
than ban » thanh ban, than man, nhuan ban
toan ban » van ban

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

• If you are trying to use Boolean operators, they must be ALL CAPS: hoc hieu manh - canh trinh quan ((dung cong) OR (bang song)) dan ((than ban) OR (toan ban))~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc hieu manh - canh trinh quan ((dung cong) or (bang song)) dan ((than ban) OR (toan ban))~".
• Adding a wildcard symbol may retrieve word variants: hoc hieu manh - canh trinh quan ((dung cong) or (bang song)) dan ((than ban) OR (toan ban))*.