deletions | additions       diff --git a/ball.md b/ball.md  index 56fe29c..22f5013 100644  --- a/ball.md  +++ b/ball.md 
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####Some Image above reproduced from http://bl.ocks.org/mbostock/4062085   You should be able to use the left and right arrow keys to move the graph. You might have to click on the graph to gain focus.     Some  online articles now let one rotate 3d figures. We can do better: