From the Kharkiv Forum:
Question: Adult cats (over 10 years old), sterilized. There is a competition "Who is the most". Going to the toilet on a pot is equal to a celebration. Any attempt to get rid of it is ignored. Tested all kinds of sprays and liquids, orange and lemon crusts, were "and knot, and spice". The problem has gained threatening proportions. You cannot live this way. Advice what to do? I sit down and decide: either sleep or let go.

Answer: "Write in their toilet. Cats have a very developed sense of ownership. They will be offended, and they will be hurt where it is appropriate, so that you will not get their sort.