1. Blumberg, S. J., & Luke, J. V. (2011). Wireless substitution: Early release of estimates from the National Health Interview Survey, 〈http://www.cdc.gov/nchs/data/nhis/earlyrelease/wireless201112.pdf〉.
2. Who pays for universal service? When telephone subsidies become transparent;Crandall,2000
3. CTIA. (2011). CTIA semi-annual wireless industry survey, 〈http://www.ctia.org/advocacy/research/index.cfm/aid/10316〉.
4. Federal Communication Commission (FCC) (2004). In the matter of lifeline and link-up. Report and order and further NPR. WC docket no. 03-109. Retrieved from Federal Communication Commission website 〈http://www.fcc.gov〉.
5. Federal Communication Commission (FCC) (2006). Telephone subscribership in the U.S. (data through November 2005). Retrieved from Federal Communication Commission website 〈http://www.fcc.gov〉.