Schwarz, Christian Algorithms and Complexity, MPI for Informatics, Max Planck Society;
https://cccg.ca/proceedings/1993/Paper45.pdf (Any fulltext)
Rote, G., Schwarz, C., & Snoeyink, J. (1993). Maintaining the Approximate Width of a Set of Points in the Plane. In Proceedings of the 5th Canadian Conference on Computational Geometry (pp. 258-263).