1. Rob Flaherty, Google Analytics plug-in (Riveted), see http://riveted.parsnip.io/.
2. Rob Flaherty, Google Analytics plug-in (Scroll Depth), see http://scrolldepth.parsnip.io/.
3. Suresh K. Gorakala, Michele Usuelli, Building a Recommendation System with R, (Packet Publishing, 2015), pp. 53–73.
4. Michael Hahsler, Recommenderlab: A Framework for Developing and Testing Recommendation Algorithms, see https://cran.r-project.org/web/packages/recommenderlab/vignettes/recommenderlab.pdf.
5. Hosein Jafarkarimi; A.T.H. Sim and R. Saaadatdoost, “A Naïve Recommendation Model for Large Database”, International Journal of Information and Education Technology (June 2012).