The Dade group of (almost) extraspecial <f>p</f>-groups

In this paper, we determine a presentation by explicit generators and relations for the Dade group of all (almost) extraspecial <f>p</f>-groups. The proof of the main result uses the cohomological properties of the Tits building corresponding to the natural geometric structure of the lattice of subgroups of such <f>p</f>-groups. [Copyright &y& Elsevier]