Table 2.

Primary study selection process.

Primary study selection process
Step 1: Selection of research repository
IEEE Xplore (IX) (270)
ScienceDirect (SD) (6,000)
Google Scholar (GS) (66,360)
Initial selection of primary studies = 72,630
Step 2: Applying exclusion criteria
Step 3: Initial selection of primary studies (80)
Step 4: Applying inclusion criteria
Step 5: Applying snowball and manual search
Step 6: Applying inclusion/exclusion criteria again
Step 7: Applying a checklist
Finally, a total of 39 primary studies were selected for data extraction and further analysis.