@incollection{rahel2008papst,
  author = {Oesterle, Jenny Rahel},
  title = {Papst – Kalif – König. Vergleiche sakraler Herrschaftsformen im Spiegel islamischer und christlicher Quellen des Mittelalters und moderner Forschung},
  booktitle = {Transkulturelle Komparatistik. Beiträge zu einer Globalgeschichte der Vormoderne},
  year = {2008},
  pages = {57-72}
}

@article{LILLEY,
  author = {Lilley, Keith D.},
  title = {Cities of God? Medieval urban forms and their Christian symbolism},
  journal = {Transactions of the Institute of British Geographers},
  year = {2004},
  volume = {29},
  pages = {296-313}
}

@incollection{khnel1987earthly,
  author = {Kühnel, Bianca},
  title = {From the Earthly to the Heavenly Jerusalem. Representation of the Holy City in Christian Art of the First Millennium},
  year = {1987},
  pages = {34-38, 138-167, 174-177, 220-265, 275-279}
}