Source: https://www.amazon.com/Freedom-Principle-Experiments-Music-1965/dp/022631930X/ref=as_li_ss_tl?s=books&ie=UTF8&qid=1514370054&sr=1-1&keywords=naomi+beckwith&linkCode=sl1&tag=culturetype-20&linkId=b90782b187647c0922759c3be2d10307