Symmetric units in modular group algebras

@inproceedings{VABovdi2007SymmetricUI,
  title={Symmetric units in modular group algebras},
  author={V.A.Bovdi and L.G.Kovacs and S.K.Sehgal},
  year={2007}
}
Let p be a prime, G a locally finite p-group, K a commutative ring of characteristic p. The anti-automorphism g\mapsto g\m1 of G extends linearly to an anti-automorphism a\mapsto a^* of KG. An element a of KG is called symmetric if a^*=a. In this paper we answer the question: for which G and K do the symmetric units of KG form a multiplicative group.