1. H. Bauer, Konservative Abbildungen lokal-kompakter Räume. Math. Ann.138, 398?427 (1959).
2. N.Bourbaki, Topologie générale, Chap. I?II. Actual. Sci. et Ind.1142, Paris 1951.
3. N.Bourbaki, Topologie générale, Chap. IX (2e édition). Actual. Sci. et Ind.1045, Pars 1958.
4. L.Cesari, Surface Area. Ann. of Math. Studies35, Princeton 1956.
5. T. Iwamura, Remarks on closed mappings and compactness. Nat. Sci. Rep. Ochanomizu Univ.1, 6?8 (1951).