@patent{huttenbrink_implantierbarer_nodate,
 author = {Hüttenbrink, K. B. and Hofmann, G. and Zahnert, T. and Bornitz, M. and Blau, M.},
 title = {Implantierbarer hydroakustischer Wandler},
 number = {DE 101 63 513},
 year = {-9999},
}