Kittipob Kondee and  Chutima Prommak,  Optimal Design of Reference Node Placement for Wireless Indoor Positioning Systems in Multi-Floor Building.   journal   = {International Journal of Electronics and Communication Engineering}, [online]. World Academy of Science, Engineering and Technology.
    July 2014, vol. 91(7). 1191 - 1195
    [viewed 12 May 2021]. Available from: https://publications.waset.org/pdf/9998851.