Table 1.

Top 15 high-output countries/regions in the field.

Id	Country	Documents	Citations
1	CHINA	1,636	44,921
2	JAPAN	285	15,255
3	USA	254	15,031
4	SOUTH KOREA	140	7,654
5	GERMANY	82	3,685
6	ITALY	57	2,659
7	UNITED KINGDOM	47	2,715
8	AUSTRALIA	41	2,602
9	IRAN	37	836
10	SINGAPORE	33	2,377
11	NETHERLANDS	22	1,414
12	CANADA	22	788
13	SPAIN	19	1,458
14	SWITZERLAND	19	1,149
15	TURKEY	18	240