Positive definite functions on infinite-dimensional convex cones
H. Glöckner, Positive Definite Functions on Infinite-Dimensional Convex Cones, Providence, RI: American Mathematical Society (AMS), 2003.

Functions operating on positive semidefinite quaternionic matrices
H. Glöckner, Monatshefte Für Mathematik 132 (2001) 303–324.

Representations of cones and conelike semigroups
H. Glöckner, Semigroup Forum 60 (2000) 326–333.