\begin{thebibliography}{1}
    \bibitem{datasheet}
    Espressif Systems 
    \textit{ESP8266 Datasheet}.\\
    \texttt{https://bbs.espressif.com}, 2015.\\

    \bibitem{reference}
    Espressif Systems
    \textit{ESP8266 Technical Reference}.\\
    \texttt{https://bbs.espressif.com}, 2017.\\

    \bibitem{kolban}
    <NAME>.
    \textit{Kolban's Book on the ESP32 \& ESP8266}. \\
    \texttt{https://www.neilkolban.com/tech/}, Texas, USA, 2016.\\

    \bibitem{olimex}
    OLIMEX \textsuperscript{\textcopyright}.
    \textit{How to use ESP8266 with Arduino IDE}.\\
    \texttt{https://www.olimex.com/}, 2017.\\

    \bibitem{at_instruction_set}
    Espressif Systems.
    \textit{ESP8266. AT Instruction Set}.\\
    \texttt{https://www.espressif.com}, 2019.\\

    \bibitem{espressif_guide}
    Espressif Systems.
    \textit{ESP8266 SDK. Getting Started Guide}.\\
    \texttt{https://www.espressif.com}, 2019.\\

\end{thebibliography}