“…Of included studies -in the period of 1970 to 2019-the US researchers conducted the most studies [26][27][28][29][30][31]. Other countries according to the number of studies were as follow: UK [32][33][34][35], Germany [10,36,37], Denmark [8,38], Iran [39,40], India [41,42], China [43], Croatia [44], Italy [45], Brazil [46], Philippines [47], Lithuania [48], and Poland [6]. However, it appears that some of these studies from Germany [10,36,37], Denmark [8,38], Iran [39,40] and the US [27,29] are sub-projects conducted within the framework of a larger and more comprehensive program.…”