RAJNIK, E. Professor Bernard Piotrowski zum 70. Geburtstag. Folia Scandinavica Posnaniensia, [S. l.], v. 10, p. 5–10, 2009. Disponível em: https://pressto.amu.edu.pl/index.php/fsp/article/view/3563. Acesso em: 29 jan. 2023.