... Therefore, the present systematic review and trend analysis can become a guidance platform for researchers, educators, policymakers or even journal publishers for future research in PLEs research. The current systematic review is significant and Self-regulated learning [7], [38[, [41], [43], [48], [54], [56], [57], [63], [64], [67], [68], [78], [86], [88], [91], [102], [104], [111], [113], [115], [119], [121], [122], [132]- [134], [136], [137], [139]- [141], [143], [145], [147], [168]- [173] Self-efficacy [105] Self-directed learning [35], [42], [47], [55], [62], [65], [66], [75], [85], [98], [120], [142], [150], [154]- [157[, [174] Transformational leadership and constructivism [175] Constructivism [33], [39], [45], [49], [79], [84], [91], [93], [99], [101], [123], [127], [131], [138[, [159] Connectivism & self-regulated learning [75] Self-learning [87], [103], [128], [176] Socio-cultural theory [50] Lifelong learning [125], [151], 161] TAM [61] Connectivism [51], [144], [158] Constructivism & Connectivism [76] Self-Reported Learning [149], [177] Self-directed + Connectivism [53] Lifelong theory [59] Technology-enhanced learning [178] Personal construct theory [179] Technology acceptance models [152] Self-disclosure learning [129] Situated Learning [82] Collaborative learning [106] Constructivism+ Searle"s theory [112] Mobile learning theories [72] Epistemological [180] IX. CONCLUSION indispensable in reviewing journal articles that discussed PLEs between 2000 and 2020. ...