An outbreak of listeriosis due to Listeria monocytogenes serotype 3a from butter in Finland Autio, T and Lyytikäinen, O and Maija, H and Riitta, M and P Ruutu and J Mikkola and A Siitonen, Weekly releases (1997–2007), 3, 1437 (1999), https://doi.org/10.2807/esw.03.11.01437-en