Herzberger, J. “Über Einige intervallmässige Iterationsverfahren: On Some Interval-Based Iterative Methods”. Anal. Numér. Théor. Approx. 8, no. 1 (February 1, 1979): 53–57. Accessed September 3, 2025. https://www.ictp.acad.ro/jnaat/journal/article/view/1979-vol8-no1-art6.