Sources

SAR jtree joshuatree search-and-rescue cave team climbing california
http://eecue.com/p/25136/truit-lead-climbing.html

Keeping Climbers Alive With Physics
http://physicsbuzz.physicscentral.com/2015/01/keeping-climbers-alive-with-physics.html

Climbing Anchors and the Evolution of the Quad
http://www.rockandice.com/climbing-news/climbing-anchors-and-the-evolution-of-the-quad