Bryła, Marek, Grzegorz Stegienta, Alina Kowalska, and Irena Maniecka-Bryła. 2009. “Internet As a Source of Information in Public Health. Part II.The Most Popular Internet Services Related to Public Health Information”. Polish Journal of Public Health 119 (4): 428-35. https://czasopisma.umlub.pl/pjph/article/view/2432.