K-groups and L-groups are obstructions to geometric structure in homotopy, via Whitehead torsion and the Wall finiteness and surgery obstructions.
Andrew Ranicki, lower k- and l-theory

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K-groups and L-groups are obstructions to geometric structure in homotopy, via Whitehead torsion and the Wall finiteness and surgery obstructions.
Andrew Ranicki, lower k- and l-theory