Map of the new Cambridge Subway in 1912
Electric Railway Journal
"<a rel="nofollow" class="external text" href="https://books.google.com/books?id=WxY6AQAAMAAJ&amp;pg=PA782&amp;lpg=PA782#v=onepage&amp;q&amp;f=false">The Cambridge Subway</a>", Electric Railway Journal, May 11, 1912