Unfinished business: Billie Jean King still learning, and inspiring, at 81

In theory, Billie Jean King should have nothing left to prove. But at 81, she’s back in college, working to finish her degree.

​ In theory, Billie Jean King should have nothing left to prove. But at 81, she’s back in college, working to finish her degree. Read More Breaking News, Latest News and Videos | CNN