# nLab Nicolaas Kuiper

## Selected writings:

Proof of Kuiper's theorem (that U(ℋ) is contractible in the norm topology):

• Nicolaas Kuiper, Contractibility of the unitary group in Hilbert space, Topology, 3, 19-30 (1964)

On microbundles:

• Nicolaas Kuiper, The quotient space of $\mathbb{C}P(2)$ by complex conjugation is the 4-sphere, Mathematische Annalen, 1974 (doi:10.1007/BF01432386)
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