Pontryagin duality for convergence groups of unimodular continuous functions Heinz-Peter Butzmann — 1983 Czechoslovak Mathematical Journal
Sequentially determined convergence spaces Ronald Beattie; Heinz-Peter Butzmann — 1987 Czechoslovak Mathematical Journal
Filter convergence via sequential convergence Ronald Beattie; Heinz-Peter Butzmann; Horst Herrlich — 1986 Commentationes Mathematicae Universitatis Carolinae