Central Transportation Planning Staff (January 2004) [May 2003]. "Chapter 5C: Service Expansion"(PDF). 2004 Program for Mass Transportation. Boston Metropolitan Planning Organization. Archived from the original(PDF) on 20 February 2012. Retrieved 17 July 2012.
Central Transportation Planning Staff (January 2004) [May 2003]. "Chapter 5C: Service Expansion"(PDF). 2004 Program for Mass Transportation. Boston Metropolitan Planning Organization. Archived from the original(PDF) on 20 February 2012. Retrieved 17 July 2012.