@ARTICLE{cg2014, author = {C. Carstensen and D. Gallistl}, title = {Guaranteed lower eigenvalue bounds for the biharmonic equation}, journal = {Numer. Math.}, year = {2014}, volume = {126}, pages = {33--51}, number = {1}, doi = {10.1007/s00211-013-0559-z}, fjournal = {Numerische Mathematik} }