TABLE 2.
Periods and documents per period.
| Period number | Period | Number of documents |
| 1 | 2009–2017 | 19 |
| 2 | 2018 | 22 |
| 3 | 2019 | 32 |
| 4 | 2020 | 29 |
Source: Own elaboration from SciMAT data.
Official websites use .gov
A
.gov website belongs to an official
government organization in the United States.
Secure .gov websites use HTTPS
A lock (
) or https:// means you've safely
connected to the .gov website. Share sensitive
information only on official, secure websites.