Advances in non-Archimedean Analysis. 13th international conference on p-adic functional analysis, University of Paderborn, Paderborn, Germany, August 12--16, 2014
H. Glöckner, A. Escassut, K. Shamseddine, eds., Advances in Non-Archimedean Analysis. 13th International Conference on p-Adic Functional Analysis, University of Paderborn, Paderborn, Germany, August 12--16, 2014, 2016.

Convolution algebras which are not necessarily positivity-preserving
M. Rösler, in: Applications of Hypergroups and Related Measure Algebras, American Mathematical Society, Providence, Rhode Island, 1995, pp. 299–318.