Agnes Beena, T. Lucia; Poongodi, T.; Suresh, P.: 'Smart e-learning transition using big data: perspectives and opportunities' (Computing, 2021), 'E-learning Methodologies: Fundamentals, technologies and applications', Chap. 7, pp. 147-173, DOI: 10.1049/PBPC040E_ch7
IET Digital Library, https://digital-library.theiet.org/;jsessionid=1kug2se8ahov2.x-iet-live-01content/books/10.1049/pbpc040e_ch7