Cătinaş, E., & Păvăloiu, I. (1997). On approximating the eigenvalues and eigenvectors of linear continuous operators. Rev. Anal. Numér. Théor. Approx., 26(1), 19–27. Retrieved from https://ictp.acad.ro/jnaat/journal/article/view/1997-vol26-nos1-2-art3