Friedrichs, Stephan Algorithms and Complexity, MPI for Informatics, Max Planck Society;
http://jocg.org/index.php/jocg/article/view/242 (Verlagsversion)
Friedrichs, S., Hemmer, M., King, J., & Schmidt, C. (2016). The Continuous 1.5D Terrain Guarding Problem: Discretization, Optimal Solutions, and PTAS. Journal of Computational Geometry, 7(1), 256-284.