Is it possible to keep avocados from turning brown?

http://www.huffingtonpost.com/2012/01/10/keeping-avocados-from-turning-brown_n_1196633.html

Claims
http://foodreference.about.com/od/Tips_Techniques/a/How-To-Keep-Avocados-From-Turning-Brown.htm
http://www.naturalnews.com/028888_avocado_avocados_health.html
http://truthaboutabs.blogspot.ca/2014/08/tip-how-to-keep-cut-avocado-from.html