Babič, Matej, et al. “New Method for Constructing a Visibility Graph-Network in 3D Space and a New Hybrid System of Modeling”. Computing and Informatics, vol. 36, no. 5, Dec. 2017, pp. 1107-26, http://147.213.75.17/ojs/index.php/cai/article/view/2017_5_1107.