[1] Schwabik Š.: 
On an integral operator in the space of functions  with bounded variation. Časopis pěst. mat. 97(1972), 297-330. 
MR 0450906 | 
Zbl 0255.47057[2] Schwabik Š.: 
On Volterra-Ѕtieltjes integral equations. Časopis pěst. mat. 99 (1974), 255 - 278. 
MR 0361661[3] Schwabik Š.: 
On an integral operator in the space of functions with bounded variation, II. Časopis pěst. mat. 102 (1977), 189-202. 
MR 0450907 | 
Zbl 0355.47033