## 4 Bibliographic Research  
Our bibliographic research was conducted using the Scopus and Google Scholar platforms, focusing on results related to wireless sensor networks in critical infrastructures. Initially, we retrieved several thousand results. However, to refine our search, we applied filters based on publication dates (2019-2023) and on keywords such as \"Critical Infrastructure WSN\", \"critical WSN\", and \"CI sensor networks\", significantly reducing the number of results. Throughout our bibliographic research, we frequently encountered the term \"critical\" used in various contexts, such as \"critical applications\", \"critical timing\", \"critical areas\", and \"critical demands\". However, these instances often did not directly pertain to the specific and highly relevant concept of \"critical infrastructure\". As our study delved deeper into critical infrastructures, it became increasingly apparent that, for a more focused and relevant analysis, it was crucial to selectively examine publications that explicitly referred to \"critical infrastructure\" as a distinct term. To accomplish this, detailed and precise examination of the term \"Critical Infrastructures\", and specifically studying \"Wireless Sensor Networks\", we undertook additional steps to enhance the quality of our research. These steps included omitting duplicate papers, excluding those with identical titles, and eliminating those with insufficient or less-relevant content. Throughout our research, we remained focused on individual papers that addressed our primary criteria and aligned with the objectives outlined in the introduction. Consequently, we narrowed down our references to a total of 22 papers (Table 2). The term \"general reference\" is used to describe studies that provide a brief and general mention of a CI sector without delving into detailed analysis or exploring specific scenarios and characteristics of that sector. This approach often lacks depth and a comprehensive understanding of the unique aspects and challenges within each CI sector. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Citation** & **Reference Number** & **CI Sector** & **Wireless Communication** & **Standards** & **Type of Paper** & **Year** \\ \hline
63 & [41] & Water & ZigBee and 4G wireless & - & Journal Article & 2019 \\ \hline
26 & [42] & Water & ZigBee and 4G & - & Journal Article & 2020 \\ \hline
26 & [43] & Energy & 5G & - & Journal Article & 2021 \\ \hline
1 & [44] & Transportation Sector & 5G & - & Journal Article & 2023 \\ \hline
1 & [46] & Energy & ZigBee & IEEE 802.15.4 & Conference Paper & 2020 \\ \hline
10 & [47] & Energy & ZigBee/LoRaWAN & - & - & Journal Article & 2021 \\ \hline  & & & & ISO 37120, ISO 37122 & & \\  & & & & ISO 37120, ISO 37123 & & \\
22 & [49] & Water & NB-IoT & ISO/ICE 2001-207 & Journal Article & 2023 \\  & & & & & in RD 2/11, & \\  & & & & ISO 27002 & & \\ \hline
2 & [50] & Industrial/Manufacturing & NB-IoT & 3 GPP standardization & Conference Paper & 2020 \\ \hline  & [53] & Health Industrial Transportation & LoRaWAN & - & Journal Article & 2022 \\ \hline - & [54] & Industrial/Manufacturing & LoRaWAN & - & Conference Paper & 2021 \\ \hline - & [55] & Military, Emergency/Rescue Services & LoRaWAN, Helium & AES-128 & Conference Paper & 2023 \\ \hline
6 & [58] & Health & Bluetooth Low Power & - & Journal Article & 2022 \\ \hline - & [60] & Energy & ZigBee PRO, WirelessHART, and ISA & & & \\  & & & 100.11a. & - & Journal Article & \\ \hline  & & & General Reference to & & & \\
20 & [66] & Smart Grids, Intelligent Transport Systems, & & & & \\  & & Healthcare and Medical, & & & \\  & & Industrial/Manufacturing & & & & \\ \hline
18 & [67] & General Reference to & & & & \\  & & healthcare & & & & \\ \hline  & & & General Reference to Critical Public & & & \\
9 & [68] & Infrastructure & Energy & General Reference to 6 LowPAN & - & Journal Article & 2020 \\  & & Transport & Health & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Bibliographic research.