@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}
}