Importance of copper minerals
http://camillacastro.us/forums/profile.php?id=11380
Producing Copper from Recycled Sources
http://www.schalke04.cz/forum/viewthread.php?thread_id=115168
Copper in Additive Manufacturing: Newbie on the Rise
http://360photography.co.uk/forum/viewtopic.php?f=4&t=2356040
What is Copper Metal Used For?
http://game.776.tw/viewthread.php?tid=655508&page=1&authorid=603042
Top 15 Copper Producing Countries in The World
http://game.776.tw/viewthread.php?tid=1139882&extra=
What can we learn from the rapid decline of copper?
http://permitbeijing.com/forum/showthread.php?tid=1654728
