Mullan, Jeffery B. (January 22, 2010). "Re: Urban Ring Phase 2, EOEEA #12565"(PDF). Massachusetts Executive Office of Energy and Environmental Affairs. Archived from the original(PDF) on March 23, 2020. Retrieved October 31, 2019.
"Urban Ring Phase 2: Fact Sheet", Executive Office of transportation, Commonwealth of Massachusetts, January 2009 (archived 2011)
Mullan, Jeffery B. (January 22, 2010). "Re: Urban Ring Phase 2, EOEEA #12565"(PDF). Massachusetts Executive Office of Energy and Environmental Affairs. Archived from the original(PDF) on March 23, 2020. Retrieved October 31, 2019.