Towards measuring the informal city: a societal metabolism approach - Smit, Suzanne (Stellenbosch University. School of Public Leadership (South Africa)) ; Musango, Josephine K. (Stellenbosch University. School of Public Leadership (South Africa)) ; Kovacic, Zora (Universitat Autònoma de Barcelona. Institut de Ciència i Tecnologia Ambientals) ; Brent, Alan C. (Victoria University of Wellington. Engineering and Computer Science (New Zealand))