Groze, S. “The Principle of the Majorant in Solving Operator Equations Which Depend on Parameters”. 1979. J. Numer. Anal. Approx. Theory, vol. 8, no. 2, June 2022, pp. 177-80, https://ictp.acad.ro/jnaat/journal/article/view/1979-vol8-no2-art7.