Conference report of the 9th Czechoslovak colloquium on number theory : [Račkova Dolina September 1989, mathematical institute of the Slovak academy of sciences, department of mathematics of the agricultural University in Nitraand Department of mathematics of the faculty of sciences of the J. E. Purkyně University in Brno : sborník : určeno pro posl. přírodovědecké fak.] / [úvod Š. Porubský, L. Skula] .  Brno :  Masarykova univerzita,  1990 .  122 s.