Sipilä, T. and Hyvärinen, H. 1998. Status and biology of Saimaa (<i>Phoca hispida saimensis</i>) and Ladoga (<i>Phoca hispida ladogensis</i>) ringed seals. NAMMCO Scientific Publications. 1, (Jun. 1998), 83–99. DOI:https://doi.org/10.7557/3.2982.