Media type: E-Article Title: Generalised energy conservation law for wave equations with variable propagation speed Contributor: Hirosawa, Fumihiko; Wirth, Jens Published: Elsevier BV, 2009 Published in: Journal of Mathematical Analysis and Applications, 358 (2009) 1, Seite 56-74 Language: English DOI: 10.1016/j.jmaa.2009.04.048 ISSN: 0022-247X Keywords: Applied Mathematics ; Analysis Origination: Footnote: Access State: Open Access