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• [2] Hellmuth Kneser, Die Deformationssätze der einfach zusammenhängenden Flächen, Math. Z. 25 (1926), no. 1, 362–372 (German). MR 1544816, http://dx.doi.org/10.1007/BF01283844
• [3] J. Munkres, Differentiable isotopies on the two-sphere, Abstract 548-137, Notices Amer. Math. Soc. vol. 5 (1958) p. 582.
• [4] R. Thom, Les singularités des applications différentiables, Ann. Inst. Fourier, Grenoble 6 (1955–1956), 43–87 (French). MR 0087149 (19,310a)

Bibliography

[1]

J. L. Kelley, General topology, New York, 1955. MR 0070144 (16:1136c)

[2]

H. Kneser, Die Deformationssätze der einfach zusammenhängenden Flacher, Math. Z. vol. 25 (1926) pp. 362-372. MR 1544816

[3]

J. Munkres, Differentiable isotopies on the two-sphere, Abstract 548-137, Notices Amer. Math. Soc. vol. 5 (1958) p. 582.

[4]

R. Thom, Les singularites das applications differentiables, Ann. Inst. Fourier, Grenoble vol. 6 (1956) pp. 43-87. MR 0087149 (19:310a)