Linearity and Unprovability of Set Union Problem Strategies. I. Linearity of Strong Postorder.

Martin Loebl Jaroslav Nesetril Linearity and Unprovability of Set Union Problem Strategies. I. Linearity of Strong Postorder. 207-220 1997 23 J. Algorithms 2 db/journals/jal/jal23.html#LoeblN97