1 http://rewriting-the-rules.com/2015/02/13/bdsm-101-consent-consent-consent/
2 http://www.datenschlag.org/txt/safco.html
3 https://www.youtube.com/watch?v=TD2EooMhqRI
4 Roach, M. Bonk, The curious coupling of sex and science, Canongate Books Ltd; 2009