@unpublished{multiindex,
    AUTHOR = {Dick, Josef and Feischl, Michael and Schwab, Christoph},
     TITLE = {Improved Efficiency of a Multi-Index {FEM} for Computational Uncertainty Quantification },
   NOTE = {arXiv preprint 1806.04159},
      YEAR = {2018},
      URL = {https://arxiv.org/abs/1806.04159}
}