Table 2. Search result and filtering divided by source.
| Search engine | Springer | IEEE | CONRICYT | Schoolar Google | arXiv | DOAJ | Total |
|---|---|---|---|---|---|---|---|
| Search results | 593 | 889 | 319 | 900 | 293 | 184 | 3,178 |
| Candidates | 583 | 864 | 306 | 881 | 278 | 171 | 2,912 |
| Primary studies | 4 | 13 | 4 | 8 | 5 | 5 | 39 |
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