Cole, Stuart, Torben Holvad, Thaddaeus O’Higgins, e Michael Gommers. «Evaluation of Rail Services». Proceedings from the Annual Transport Conference at Aalborg University 4, no. 1 (Dezembro 31, 1997). Acedido Julho 3, 2024. https://journals.aau.dk/index.php/td/article/view/4034.