Table 4.

The number and percentage of papers containing studies at each number of dosing levels.

Number of Papers (%)	Number of Dose Levels	Paper References
21 (60%)	3	[17,19,22,24,25,27,28,29,30,32,34,35,37,38,42,44,46,48,49,40]
8 (23%)	4	[16,20,21,23,26,36,40,43]
5 (14%)	5	[18,33,39,41,45]
1 (3%)	6	[31]
1 (3%)	7	[47]