Perhaps you should try some spelling variations:
hanh trinh » canh tranh, hanh chinh
chieu sang » chieu sach, chieu xanh, nhieu tang
thong cong » tong cong, thong thong, phong chong
hieu lang » hieu quang, nhieu tang, hieu van
trinh cua » tinh cua, trinh luat, trinh quan
tap toan » tap doan, tap quan, bai toan
toan cau » toan cao, toan ban, toan tap

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: ho ((chieu sang) OR (hieu lang)) - hanh trinh cua ((thong cong) OR (trong cong)) tap toan cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "ho ((chieu sang) or (hieu lang)) - hanh trinh cua ((thong cong) OR (trong cong)) tap toan cau~".
• Adding a wildcard symbol may retrieve word variants: ho ((chieu sang) or (hieu lang)) - hanh trinh cua ((thong cong) OR (trong cong)) tap toan cau*.