http://ella-p.livejournal.com/705631.html?thread=4847199#t4847199 !!!!!!!!!!!
http://academics.hamilton.edu/government/home/2002//faculty/swrivera.html
http://www.maxwell.syr.edu/moynihan/programs/ces/pcconfpdfs/Rivera.pdf
http://ella-p.livejournal.com/705631.html?thread=4874079#t4874079
