Table 3.

Most used recommendation techniques in the e-learning domain

Recommendation method	Citation
Ontology-Based	Fraihat and Shambour (2015), Saleena and Srivatsa (2015), Labib et al. (2017), Ouf et al. (2017), Bouihi and Bahaj (2019), and Joy et al. (2019)
Collaborative Filtering	Dwivedi and Bharadwaj (2015), Bourkoukou and El Bachari (2016), Bourkoukou et al. (2016), Klašnja-Milićević et al. (2018a), and Segal et al. (2019)
Content-Based	Albatayneh et al. (2018), Dwivedi et al. (2018), and Nabizadeh et al. (2020)
Hybrid	Senthilnayaki et al. (2015), Tarus et al.(2017), Bourkoukou et al. (2017), Benhamdi et al. (2017), Tarus et al.,(2018a, 2018b), Nafea et al. (2018), Christudas et al.(2018), Wan and Niu (2018), Klašnja-Milićević et al. (2018a), Xiao et al. (2018), Deng et al. (2018),Aeiad and Meziane (2019), Sarwar et al. (2019), Bhaskaran and Santhi (2019), Wan and Niu (2019), Nafea et al. (2019),Riyahi and Sohrabi (2020), Ibrahim et al. (2020), Venkatesh and Sathyalakshmi (2020), Murad et al. (2020), Al Abri et al. (2020), Nihad et al. (2020), Anuradha et al. (2020), and Hwang et al.(2020a)
Group-based	Rahman and Abdullah (2018)
Rule-Based	Wan and Niu (2016), Dorca et al. (2016), and Kolekar et al. (2019)
Skill-based	Jagadeesan and Subbiah (2020)