Perhaps you should try some spelling variations:
tranh thai » trang thai, tran thi, tinh thai
doi chieu » doc hieu, doi chi, mot chieu
thai vung » thai cong, thai van
vung cong » dung cong, vung dong, vung song
ho chieu » theo chieu, hoc thieu, mot chieu
tam toan » tam than, pham toan, tam thanh
tap toan » tap doan, tap quan, bai toan

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) OR (doi chieu)) xanh - canh tranh thai vung cong ((tam toan) OR (tap toan)) cau~.
• The words AND, OR and NOT may confuse the search; try adding quotes: "((ho chieu) OR (doi chieu)) xanh - canh tranh thai vung cong ((tam toan) or (tap toan)) cau~".
• Adding a wildcard symbol may retrieve word variants: ((ho chieu) OR (doi chieu)) xanh - canh tranh thai vung cong ((tam toan) or (tap toan)) cau*.