K. S. Gulak, “Friendship – the value of personal relationships in different periods of human of the life of human beings”, piel21w, vol. 11, no. 1(38), pp. 73–77, Jan. 2012, Accessed: Jun. 08, 2025. [Online]. Available: https://czasopisma.umlub.pl/piel21w/article/view/2713