@inproceedings{g2013proceed,
author = {D. Gallistl},
title = {An optimal adaptive {FEM} for eigenvalue clusters},
booktitle= {Oberwolfach Reports},
year = {2013},
volume = {10},
number = {4},
pages = {3267--3270},
doi = {10.4171/OWR/2013/56},
}