The development of the telephone in Oxford 1877-1977 / R. A. J. Earl
Telephony : a detailed exposition of the telephone exchange systems of the British Post Office / J. Atkinson
Introduction to congestion theory in telephone systems / R. Syski; pref. Sir thomas Eads; 2º Capítulo por N. H. G. Morris
Tele-communications in Germany : an economic perspective / Günter Pfeiffer, Bernhard Wieland