P. Oliver, G. Baird, M. Cook, L. Johnson, and P. Hoyt. AFIPS National Computer Conference, volume 43 of AFIPS Conference Proceedings, page 431-438. AFIPS Press, (1974)
P. Cook. AFIPS Spring Joint Computing Conference, volume 30 of AFIPS Conference Proceedings, page 779-782. AFIPS / ACM / Thomson Book Company, Washington D.C., (1967)