An open three-manifold which is simply connected but is topologically distinct from Euclidean three-space.
Whitehead Manifold
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References
Rolfsen, D. Knots and Links. Wilmington, DE: Publish or Perish Press, p. 82, 1976.Referenced on Wolfram|Alpha
Whitehead ManifoldCite this as:
Weisstein, Eric W. "Whitehead Manifold." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/WhiteheadManifold.html