By Unknown – Retrieved October 20, 2014 from Telephony magazine, Telephony Publishing Co., Chicago, Vol. 73, No. 10, September 8, 1917, p. 33 on Google Books, Public Domain, https://commons.wikimedia.org/w/index.php?curid=36293858
By Unknown – Retrieved October 20, 2014 from Telephony magazine, Telephony Publishing Co., Chicago, Vol. 73, No. 10, September 8, 1917, p. 33 on Google Books, Public Domain, https://commons.wikimedia.org/w/index.php?curid=36293858