Table 3.

Popularity of the topic in the digital library.

Digital Library	O(G)D	Sensor			Real-Time			COVID-19
		Total	Primary	Ratio	Total	Primary	Ratio	Total	Primary	Ratio
ACM Digital Library	961	375	61	6.35%	745	181	0.19%	61	4	0.42%
IEEE Xplore	1308	343	102	7.8%	350	60	0.05%	15	8	0.61%
Science Direct	224	310	43	1.85%	618	86	0.04%	35	19	0.81%
Emerald Insight	154	24	1	0.65%	4	2	0.01%	2	0	0