Janusz Łętowski, Les problèmes juridiques de la direction dans l’administration, Wrocław 1977, Ossolineum. Contemporary Central & East European Law, [S. l.], n. 3 (35), p. 38–40, 1977. Disponível em: https://czasopisma.inp.pan.pl/index.php/cceel/article/view/1471. Acesso em: 7 oct. 2025.