## 3 Results  
### Performance and Scientific Production  
Scientific production on ARHE (n = 552) dates back to 1997 (n = 2) and has remained uninterrupted until the present, albeit with a variable amount of documentation, which is irregular from 1998 (n = 1) until 2014 (n = 23), due to increases and decreases in publications (1999--n = 1; 2000--n = 5; 2001--n = 2; 2002--n = 4; 2003--n = 5; 2004--n = 4; 2005--n = 6; 2006--n = 6; 2007--n = 2; 2008--n = 6; 2009--n = 10; 2010--n = 18; 2011--n = 15; 2012--n = 29; 2013--n = 25). On the other hand, from 2015 (n = 52) onwards, the ascent is prominent (2016--n = 70; 2017--n = 94; 2018--n = 111; 2019--n = 61). Figure 2 shows the evolutionary development of ARHE throughout its history in the scientific literature. This figure shows three clearly differentiated periods. During the first period, which covers from 1997 to 2007, there is low and uniform production. During the second stage, from 2008 to 2014, the level of production rises irregularly. Finally, in the third period, the production is ascending and more abundant compared to previous periods. The development for 2019 is not significant, since the natural end of the year has not yet occurred, with the literature being open to the publication of new scientific works. \begin{table}
\begin{tabular}{c c} \hline \hline
**Configuration** & **Values** \\ \hline Analysis unit & Keywords authors, keywords WoS \\ \hline Frequency threshold & Keywords: P1 = (2), P2 = (3) \\  & Authors: PX = (2) \\ \hline Network type & Co-occurrence \\ \hline Co-occurrence union value threshold & Keywords: P1 = (1), P2 = (1) \\  & Authors: PX = (2) \\ \hline Normalization measure & Equivalence index \\ \hline Clustering algorithm & Maximum size: 9; Minimum size: 3 \\ \hline Evolutionary measure & Jaccard index \\ \hline Overlapping measure & Inclusion Rate \\ \hline \hline \end{tabular} Note: P1: The period from 1997 to 2015; P2: the period from 2016 to 2019; PX: the period from 1997 to 2019.  
\end{table} 
Table 2: Production indicators and inclusion criteria. Figure 2: Evolution of scientific production of augmented reality in higher education in the Web of Science (WoS). English (n = 504) is positioned as the reference language used by various researchers to show their results to the scientific community, followed, to a lesser extent, by Spanish (n = 41), Turkish (n = 3), Portuguese (n = 2), Russian (n = 2), Chinese (n = 1), French (n = 1), and German (n = 1). Regarding areas of knowledge, a reference was not obtained for studies related to ARHE, since both \"education educational research\" (n = 220) and \"computer science\" (n = 208) show similar results. ARHE is also revealed to be a topic of interest for various fields of knowledge, such as \"engineering\" (n = 144), \"telecommunications\" (n = 26), \"business economics\" (n = 20), \"social science other topics\" (n = 17), optics (n = 16), and \"imaging science photographic technology\" (n = 15). For type of document, the scientific community most commonly chooses communications (n = 315) to show the results of their research, followed, to a lesser extent, by articles (n = 235), book chapters (n = 10), literature reviews (n = 9), quick access materials (n = 2), and editorial materials (n = 2). Spanish companies have been verified as reference institutions for ARHE, given their position in Table 3. Of these, the University of la Laguna and the University of Seville are the most common world-wide references on the state of this topic. The most prolific authors include [PERSON] (n = 11), [PERSON] (n = 10), [PERSON] (n = 9), and [PERSON] (n = 7). Next most productive are [PERSON], [PERSON], [PERSON], and [PERSON], with five publications, respectively. Finally--complying with the inclusion criteria--[PERSON] has published four works. \"INTED proceedings\" is the source of origin with the highest production, followed at a considerable distance by \"EDULEARN proceedings\" and the other sources listed in Table 4.