Köppen, Manfred and Lang, Michael and Helfrich, Reiner and Steglich, Frank and Thalmeier, P. and Schmidt, B. and Wand, B. and Pankert, D. and Benner, Hartmut (1999):
Solitary magnetic excitations in the low-carrier density, one-dimensional S=1/2 antiferromagnet Yb4As3.
In: Physical review letters, p. 4548, 82, [Article]

Köppen, Manfred and Pankert, D. and Hauptmann, and Lang, Michael and Weiden, and Geibel, Christoph and Steglich, Frank (1998):
Interference of a first-order transition with the formation of a spin-Peierls state in alpha'-NaV2O5.
In: Physical review. B 57 (1998), S. 8466, [Article]