Whitehead 1949 CW-complexes built from cells via attaching-maps. Cellular-approximation theorem. Whitehead theorem: weak homotopy-equivalence between CW complexes is genuine homotopy-equivalence.
Whitehead 1949 CW-complexes built from cells via attaching-maps. Cellular-approximation theorem. Whitehead theorem: weak homotopy-equivalence between CW complexes is genuine homotopy-equivalence.