Külzer S. Formal and informal Instruments: How can they best complement each other? Exemplarily illustrated through the planning determination process and regional dialogue forum for the extension of Frankfurt Airport. RuR [Internet]. 2009 Jul. 31 [cited 2025 Jun. 15];67(4):318–329. Available from: https://rur.oekom.de/index.php/rur/article/view/985