Non-Esperanto letter X

The letter X is called ikso in Esperanto and it is not part of its alphabet.

Examples
Kromosomo X (X chromosome)

Description
Since the letter X is not part of Esperanto it is possible to simulate Esperanto's non-ASCII letters using "x", as shown in the following table:

Software that uses X-system

 * Google Translate: Accepts X-system as input.
 * Duolingo (only the exercises, not the forums): Accepts X-system as input.
 * Klavaro at Lingvo.org: http://lingvo.org/klavaro. You can type using the X-system and the letters are translated instantaneously.

Example
Unicode: Aĥ! Kaŝiĝu vi hejme! Apenaŭ uzeblas ĉi fieca langtordaĵo.

X-system: Ahx! Kaxigxu vi hejme! Apenaux uzeblas cxi fieca langtordajxo.