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I am trying to gain some intuition about retracts, deformation retracts and strong deformation retracts (see http://en.wikipedia.org/wiki/Deformation_retract for definitions). We have that any strong deformation retract is a deformation retract and any deformation retract is a retract (of course, by definition). Also, it is easy to think in a retract which is not a deformation retract.

Which are some examples of deformation retracts which are not strong deformation retracts?

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See exercise 6 on page 18 of Hatcher's book. Note the difference in terminology to Wikipedia! –  t.b. May 5 '11 at 21:56

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Similar question to this one has been asked again and an answer can be found here.

The same example but with more details can be found here.

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This should be more appropriate as a comment, IMO. –  Najib Idrissi Apr 27 at 7:21

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