Kaprekar's Process for 2-Digit Numbers/Mistake

Source Work

 * The Dictionary
 * $63$
 * $63$

Mistake

 * Kaprekar's process for $2$-digit numbers leads to the cycle $63 - 27 - 45 - 9 - 81 \ldots$

The statement needs to specify that the $2$-digit numbers do not include repdigit numbers, as for example:
 * $K \left({11}\right) = 11 - 11 = 0$

trivially.