Subspaces of Linear Spaces of Line Size 4. - Andries E. Brouwer; Hanfried Lenz (Eur. J. Comb., 1981)

Minimal linear spaces. - Dieter Jungnickel; Hanfried Lenz (J. Comb. Theory A, 1987)

A brief review on Egmont Köhler's mathematical work. - Hanfried Lenz; Gerhard Ringel (Discret. Math., 1991)