Farouk, Fifi; Rizk, Rawya; Zaki, Fayez W.: 'Multi-level stable and energy-efficient clustering protocol in heterogeneous wireless sensor networks', IET Wireless Sensor Systems, 2014, 4, (4), p. 159-169, DOI: 10.1049/iet-wss.2014.0051 IET Digital Library, https://digital-library.theiet.org/;jsessionid=175ps6tupf1nb.x-iet-live-01content/journals/10.1049/iet-wss.2014.0051