|   | 
    References 
    Sylaiou, S., Basiouka, S., Patias, P.,  Stylianidis, E., 2013. The Volunteered Geographic Information in Archaeology, ISPRS Ann. Photogramm. Remote Sens. Spatial  Inf. Sci., II-5/W1, 301-306, doi.org/10.5194/isprsannals-II-5-W1-301-2013 
    Yamaguchi,  H., Kiyama, K., Shimizu, N., Altangerel, E., 2009. Archaeological research of  the Khitai Dynasty’s Balgas City Ruins – Cultural Heritage on the Steppe Using  GIS, Proceedings of the XXII International CIPA  Symposium, 11-15 October 2009, Kyoto, Japan, www.cipaheritagedocumentation.org/wp-content/uploads/2018/12/Yamaguchi-e.a.-Archaeological-Research-of-the-Khitai-Dynasty%E2%80%99s-Balgas-City-Ruins-Cultural-Heritage-on-the-Steppe-using-GIS.pdf  | 
      |