Mechanical Advantage Series by John Middendorf aka Bigwall Scrapbook
And by the way, The American Hermann Buhl mentioned here as one of the key influencers in piton protected lead climbing is from an earlier era than the much more famous Austrian Hermann Buhl. I have been asked to make that clear!
I am getting some feedback on this one. I think one key evidence that the Colorado climbers, and not Underhill, led in terms of best rope work technique is the fact that Underhill wrote about the European around the neck rappel, while Lavender introduced what we know now as the Durfersitz, with the rope under arm. They are quite different, try them (with heavy collar jacket). The Colorado version became prevalent in the USA, and then even back in Europe in 40s.