Bai tap Be tong cot thep + vai2 tieu chuan minh vua tim.

Bai Betong cot thep!!!NH EM CAN CO TINH THAN THEP DE VUOT QUA THOI GIAN KHO KHAN NAY!!!
Tieu chuan tu gom nhat!!! hay anh em vo day down cho chac : http://tcxdvn.xaydung.gov.vn/TCXDVN/TCXDVN.NSF/START?openframeset