1. �ber Abbildung von Mannigfaltigkeiten
2. W. G. Chinn and N. E. Steenrod, First Concepts of Topology, Mathematical Association of America, Washington, D.C., 1966.
3. James Dugundji, Topology, Allyn and Bacon, Boston, 1966.
4. Marvin Greenberg, Lectures on Algebraic Topology, W. A. Benjamin, New York, 1967.
5. John W. Milnor, Topology from the Differentiable Viewpoint, University of Virginia Press, Charlottesville, 1965.