Figures:
Fig.
1 Publication output performance during 1991–2018.
Fig.
2 The collaboration of the top 20 countries/territories and
institutions: (a) network mapping of countries/territories; (b) network
mapping of institutions.
Fig.
3 Main co-cited authors for publications.
Fig.
4 Dual-map overlay of scientific publications between 1991 and 2018.
Fig.
5 Keyword co-occurrence map of publications.
Fig.
6 A cluster view of the co-citation network.
Fig.
7 A timeline visualization of the top 10 clusters.