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============ * 1 https://docs.google.com/spreadsheet/ccc?key=0Agol553XfuDZdHlWSmRRckpXZWdSczdoVVBjbHU2dHc&hl=en_GB#gid=0 (The Guardian) * 2 http://knowledge.allianz.com/mobility/transportation_safety/?813/which-transport-methods-produce-most-emissions (EEA) * 3 http://www.networkrail.co.uk/5878_Comparingenvironmentalimpactofconventionalandhighspeedrail.pdf * 4 http://www.scp-knowledge.eu/sites/default/files/knowledge/attachments/Kliucininkas%20et%20al%202012%20Life%20cycle%20assessment%20of%20alternative%20fuel%20chains%20for%20urban%20buses%20and%20trolleybuses.pdf