ISBN 978-3-030-45532-3. S2CID 166562364.[page needed] ↑ Kaviti Musango, Josephine; Currie, Paul; Smit, Suzanne; Kovacic, Zora (December 2020). "Urban metabolism of the informal city: Probing and measuring the 'unmeasurable' to monitor Sustainable Development Goal 11 indicators".