1. A reduction of the Schoenflies extension problem;Morse, Marston;Bull. Amer. Math. Soc.,1960
2. On embeddings of spheres;Mazur, Barry;Bull. Amer. Math. Soc.,1959
3. 3. J. Milnor, Differentiable manifolds which are homotopy spheres, mimeographed, Princeton, 1959.
4. Affine structures in 3-manifolds. VI. Compact spaces covered by two Euclidean neighborhoods;Moise, Edwin E.;Ann. of Math. (2),1953
5. 5. R. Penrose, J. H. C. Whitehead and E. C. Zeeman, Embedding of manifolds, to appear in Ann. of Math.