1. Isaacs R P. A finite difference function theory. Univ Nac Tucumán Revista A, 2: 177–201 (1941)
2. Isaacs R P. Monodiffric functions. In: Construction and applications of conformal maps. Proceedings of a symposium. National Bureau of Standards Appl Math Series, No. 18. Washington, DC: US Government Printing Office, 1952, 257–266
3. Ferrand J. Fonctions préharmoniques et fonctions préholomorphes. Bull Sci Math, 68: 152–180 (1944)
4. Lelong-Ferrand J. Représentation conforme et transformations intégrale de Dirichlet bornée. Paris: Gauthier-Villars, 1955
5. Jeong S. Discrete Complex Analysis. Master Thesis. Korea: Pohang University of Science and Technology, 2007