Yes, i play in translated option. And i take a look in the ufoai.mo file in my installation and there was:
enemy_on_earth_alt_txt
enemy_on_earth_pre_txt
enemy_on_earth_rev_pre_txt
enemy_on_earth_txt
but not the enemy_on_earth_rev_txt. Is there no translataion available = I can do it, but i don't found this file under translations in the wiki.