Borbála Fazekas Michael Plum Christian Wieners Enclosure for the Biharmonic Equation. 2005 conf/dagstuhl/2005P5391 Algebraic and Numerical Algorithms and Computer-assisted Proofs http://drops.dagstuhl.de/opus/volltexte/2006/448 db/conf/dagstuhl/P5391.html#FazekasPW05