Thomas Böhme John Maharry Bojan Mohar <i>K</i><sub>a, k</sub> Minors in Graphs of Bounded Tree-Width. 133-147 2002 86 J. Comb. Theory, Ser. B 1 http://dx.doi.org/10.1006/jctb.2002.2119 db/journals/jct/jctb86.html#BohmeMM02