## 4 Results  
The first result of the query using the keywords combination method explained in Section 3 shows a fairly clear gap between the number of publications on the three main topics. More than 95% of the articles deal with IoT (Table 3). A limited number of publications, less than 4%, of articles deal with BIM. Lastly, the integration of BIM and IoT is still at an early stage. Considering the number of publications on BIM and IoT integration in the last 30 years, it is possible to see how the first significant increase is registered after 2013 (Figure 2). Furthermore, publications grew almost simultaneously in both citation databases. Interestingly, 80% of the articles on Scopus and 85% of the articles on WoS were published during the last five years; this means that BIM-IoT integration is a new domain with increasing interest, especially during 2019 and 2020. Accordingly, the implementation of BIM-IoT integration for FM is also a new domain, with a limited number of publications (red line in Figure 2). Figure 2: Number of publications per year (* until February 2021) dealing with BIM and IoT in Scopus (yellow dotted), in Web of Science (blue dash-dotted) and number of product dealing with BIM and IoT for Facility Management (red dashed). \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Scopus** & **WoS** \\ \hline BIM & 3316 & 2717 \\ IoT & 157,108 & 31,088 \\ BIM + IoT & 237 & 166 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Number of journal articles on BIM, IoT and their integration resulting from Scopus and WOS databases research (until February 2021). A further query using FM core functions keywords (Table 2) was carried out to find as many articles as possible on BIM and IoT integration in the FM field. Results are shown in Table 4.  
The query was limited to journals' articles: Table 4 shows how many products were found in each database matching each FM core function with the three tools' categories. Although the contemporary use of BIM and IoT is relatively recent, some FM core functions like \"Sustainability\", \"O&M\", \"Communication\", and \"Technology\" have a significant number of publications. On the contrary, perhaps because of the novelty of the two tools' simultaneous use, some functions have a minimal number of publications. Noteworthy, \"Sustainability\" is the most studied core function even when considering BIM or IoT separately. The number of publications in the several FM core functions is relatively homogeneous if only BIM products are queried. To narrow down the scope of the review, further analysis was done on the title and abstract of each of the 904 articles dealing with BIM and IoT, discarding articles not directly related to the construction sector and FM (Table 5). Eventually, duplicates, i.e., articles covering more than one core function or present in both databases, were discarded, and the final list of 99 articles emerged. On these 99 articles published between 2013 and 2021 (Table 6), a bibliometric analysis was carried out using the R package Bibliometrix [46]. Over the period under review, and based on the proposed selection criteria, most of the articles on BIM-IoT integration for FM were published in _Automation in Construction_, with 27 of the total selected articles. Followed by: _Applied Sciences_ (6), _Journal of Computing in Civil Engineering_ (5), _Sustainability_ (5), _Advanced Engineering Informatics_ (3), _Building and Environment_ (3), _Journal of Construction Engineering and Management_ (3) and _Journal of Information Technology in Construction_ (3). The remaining journals' publication rates varied between one to two articles during the considered period. The bibliometric analysis also reveals that a significant number of publications have been conducted in the USA, with 18 publications, followed by China (12), Australia (9), Hong Kong (8), UK (7), Canada (7), Germany (6) and Italy (6). The remaining countries had less than six articles published during the considered period. Furthermore, the top 10 most cited papers are summarised in Table 7.