Hightower, David W. (1969). "A solution to line-routing problems on the continuous plane". DAC'69: Proceedings of the 6th Annual Conference on Design Automation. ACM Press. pp. 1–24. doi:10.1145/800260.809014. (NB. This contains one of the first descriptions of a "line probe router".)
Ritchey, Lee W. (December 1999). "PCB routers and routing methods"(PDF). PC Design Magazine (February 1999). Speeding Edge. Archived(PDF) from the original on 2018-10-22. Retrieved 2018-10-22.
web.archive.org
Ritchey, Lee W. (December 1999). "PCB routers and routing methods"(PDF). PC Design Magazine (February 1999). Speeding Edge. Archived(PDF) from the original on 2018-10-22. Retrieved 2018-10-22.