Title: ON YURIJ KALYUZHNYJ'S 50TH BIRTHDAY

Yurij Kalyuzhnyj was born on July 20, 1951 in Lviv. Having graduated from the Physics Department of the Lviv University in 1973 he began his work as an engineer at the Institute for Geology and Geochemistry of Fuse Fuels. In 1980 he started the postgraduate course in the Lviv Division of Statistical Physics of the Institute for Theoretical Physics under the supervision of Prof. I.R.Yukhnovskii and Prof. M.F.Holovko. His research work was devoted to the development of the site-site approach in the theory of ion-molecular systems. The results of his studies were summarized in his candidate thesis which was successfully defended in 1987.