Perhaps you should try some spelling variations:
thong cong » trong cong, tong cong, thong thong
hanh tranh » canh tranh, hanh trinh, hanh trang
tranh cua » doanh cua, manh cua
cua thong » cua thuong, cua khong, cua tong
thi hanh » thi thanh
tap toan » tap doan, tap quan
bai toan » bai tap
doi thi » doi thoi, do thi, doi khi

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

• Performing a fuzzy search may retrieve terms with similar spellings: doi thi hanh - hanh tranh cua thong cong ((tap toan) OR (bai toan)) cao~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "doi thi hanh - hanh tranh cua thong cong ((tap toan) OR (bai toan)) cao*".