A homotopy double groupoid of a Hausdorff space.
A Whitehead product for track groups (II).
Two direct relations are exhibited between the Whitehead product for track groups studied in [4] and the generalized Whitehead product in the sense of Arkowitz. The problem of determining the order of the Whitehead square is posed and some computations given.
Bivariant long exact sequences (II).
The two-square lemma.
A new proof is given of the connecting homomorphism.
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