Alstom Signaling Incorporated (2004). A Centennial: History of Alstom Signaling Inc(PDF). West Henrietta, New York: Alstom. Diarsipkan dari asli(PDF) tanggal 2 October 2011. Diakses tanggal 27 December 2011.
General Railway Signal Company (1913). Sperry, Henry M. (ed.). Electric Interlocking Handbook. Rochester, New York: General Railway Signal Company. hlm. 5–12. OCLC3527846.
Calvert, J. B. "Toucey and Buchanan Interlocking". Railways: History, Signalling, Engineering. Diarsipkan dari versi aslinya tanggal 23 April 2012. Diakses tanggal 28 December 2011.
Woolford, Paul (April 2004). Glossary of Signalling Terms(PDF) (Report). Railway Group Guidance Note GK/GN0802. London: Rail Safety and Standards Board. Diarsipkan dari asli(PDF) tanggal 8 May 2016. Diakses tanggal 20 April 2016.
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Calvert, J. B. "Toucey and Buchanan Interlocking". Railways: History, Signalling, Engineering. Diarsipkan dari versi aslinya tanggal 23 April 2012. Diakses tanggal 28 December 2011.
Alstom Signaling Incorporated (2004). A Centennial: History of Alstom Signaling Inc(PDF). West Henrietta, New York: Alstom. Diarsipkan dari asli(PDF) tanggal 2 October 2011. Diakses tanggal 27 December 2011.
Woolford, Paul (April 2004). Glossary of Signalling Terms(PDF) (Report). Railway Group Guidance Note GK/GN0802. London: Rail Safety and Standards Board. Diarsipkan dari asli(PDF) tanggal 8 May 2016. Diakses tanggal 20 April 2016.
General Railway Signal Company (1913). Sperry, Henry M. (ed.). Electric Interlocking Handbook. Rochester, New York: General Railway Signal Company. hlm. 5–12. OCLC3527846.