Separation theorems for oriented matroids. - Achim Bachem; Alfred Wanka (Discret. Math., 1988)

Euclidean intersection properties. - Achim Bachem; Alfred Wanka (J. Comb. Theory B, 1989)

On a Problem About Covering Lines by Squares. - Walter Kern; Alfred Wanka (Discret. Comput. Geom., 1990)

On adjoints and dual matroids. - Marion Alfter; Walter Kern; Alfred Wanka (J. Comb. Theory B, 1990)