Schneider, Daniel; Berent, Matt; Thomas, Randall; Krosnick, Jon (junho de 2008). «Measuring Customer Satisfaction and Loyalty: Improving the 'Net-Promoter' Score»(PDF). Measuring Customer Satisfaction and Loyalty: Improving the 'Net-Promoter' Score'. Annual Conference of the World Association for Public Opinion Research (WAPOR). Retrieved 13 August 2015 !CS1 manut: Nomes múltiplos: lista de autores (link)