Georgievska, S.S. (1995) “A BOUNDARY PROBLEM OF THE THIRD AND FOURTH ORDERS AS A PRODUCT OF BOUNDARY PROBLEMS OF THE SECOND ORDER”, Matematichki Bilten, 19(1), pp. 53–64. Available at: https://bilten.smm.org.mk/index.php/bilten/article/view/1557 (Accessed: 14 August 2026).