What is the Greatest Era of Innovation? A Guided Tour.
http://www.nytimes.com/2016/05/15/upshot/what-was-the-greatest-era-for-american-innovation-a-brief-guided-tour.html?smprod=nytcore-ipad&smid=nytcore-ipad-share NYTimes: What Was the Greatest Era for Innovation? A Brief Guided Tour