1H.Barton. Led Cluster Technology in Railway Signalling. The Sixth International Conference on"Maintenance & Renewal of Permanent Way, Power&Signalling,Structures & Earthworks", 2005
2J.Liebscher,(Siemens AG, Germany) D. Zimmermann. Source. Photo metric design of colour light signals: Signa und Draht v 96,n 12, 2004
3Petit,Williama. Wayside LED signals -Why it's harder than it looks Railway Track and Structures, 2002
4DTI, Report of a DTI global watch mission, 2005
5Petit, William A. Wayside LED signals-why it's harder than it looks. Railway Track and Structures, 2002
