Do you mean in a game that was played, a book, or the actual starting position of this endgame study?
I cannot find the source of this position

Do you mean in a game that was played, a book, or the actual starting position of this endgame study?
I mean the person who created this study and the time period. Is he Klinkov who made that position for the study?
I found this position at here (3rd answer), and it says that this is the end of Klinkov's 1966 study. But I couldn't even find this position anywhere else. I wonder the real source of this endgame position.