FARRIS, Jonathan A.. Contingency and opportunity. International Planning History Society Proceedings, [S.l.], v. 18, n. 1, p. 88-96, oct. 2018. ISSN 2468-6956. Available at: <https://journals.open.tudelft.nl/index.php/iphs/article/view/2672>. Date accessed: 16 sep. 2019. doi: https://doi.org/10.7480/iphs.2018.1.2672.