1. Borsík, J.: Local characterization of functions with closed graphs. Demonstr. Math. 29(3), 643–650 (1996)
2. Borsík, J.: Sums, differences, products and quotients of closed graph functions. Tatra Mt. Math. Publ. 24, 117–123 (2002)
3. Bourbaki, N., Diedonne, J.: Rev. Sci. 77, 180–181 (1939)
4. Doboš, J.: Sums of closed graph functions. Tatra Mt. Math. Publ. 14, 9–11 (1998)
5. Ferrer, J., Gregory, V., Alegre, C.: Extensions of semi-continuous functions. Indian J. Pure Appl. Math. 26(2), 103–112 (1995)