Perhaps you should try some spelling variations:
trinh chuan » trinh han, trinh quan, trinh luan
canh trinh » canh tranh, hanh trinh, canh tinh
chieu xanh » chieu sach, chieu sang, chieu tinh
hieu manh » hieu nganh, dieu hanh, hien hanh
dung cong » dung trong
bang song » nang song
dan toan » van toan, dan than, manh toan
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) OR (chieu xanh)) - canh trinh chuan ((dung cong) OR (bang song)) dan toan ban~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "hoc ((hieu manh) OR (chieu xanh)) - canh trinh chuan ((dung cong) or (bang song)) dan toan ban~".
• Adding a wildcard symbol may retrieve word variants: hoc ((hieu manh) OR (chieu xanh)) - canh trinh chuan ((dung cong) or (bang song)) dan toan ban*.