Pohrybieniuk, J., A. Krotliński, A. Dusińska, J. Sokołowska, and M. Chabowski. “Loneliness Among Surgical Patients - Measuring Levels of Loneliness Using De Jong Gierveld Loneliness Scale and Revised UCLA Loneliness Scale”. Journal of Education, Health and Sport, vol. 12, no. 12, Dec. 2022, pp. 303-10, doi:10.12775/JEHS.2022.12.12.046.