Verfuß, U. K., Honnef, C. G., Meding, A., Dähne, M., Mundry, R., & Benke, H. (2007). Geographical and seasonal variation of harbour porpoise (Phocoena phocoena) presence in the German Baltic Sea revealed by passive acoustic monitoring. Journal of the Marine Biological Association of the UK, 87(1), 165-176. doi:10.1017/S0025315407054938.