Classification of the simple factors appearing in composition series of totally disconnected contraction groups
H. Glöckner, G.A. Willis, Journal Für Die Reine Und Angewandte Mathematik 643 (2010) 141–169.

Directions of automorphisms of Lie groups over local fields compared to the directions of Lie algebra automorphisms
H. Glöckner, G.A. Willis, Topology Proceedings 31 (2007) 481–501.

Contraction groups for tidy automorphisms of totally disconnected groups
H. Glöckner, Glasgow Mathematical Journal 47 (2005) 329–333.