M.Stella and  M. Russo and  D. Begušić,  GSM-Based Approach for Indoor Localization.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    April 2013, vol. 76(4). 374 - 378
    [viewed 12 July 2020]. Available from: https://publications.waset.org/pdf/11848.