KAMPMANN, Ricarda. Patent applications in the Ruhr area — Strengths and weaknesses compared by agglomerations. Raumforschung und Raumordnung | Spatial Research and Planning, DE, v. 66, n. 5, p. 440–449, 2008. DOI: 10.1007/BF03183187. Disponível em: https://rur.oekom.de/index.php/rur/article/view/1232. Acesso em: 15 aug. 2026.