"Sono scritti sia anteriormente che posteriormente."
This translation is weird, to say the least. A better, more common one would be "Sono scritti sia sul davanti che sul dietro". Forget about "anteriormente" and "posteriormente" they are almost never used. We say "La parte posteriore e la parte anteriore dell'auto" (front and back part of the car), but the adverb is so rare...
Thank you but I wonder, perhaps as does makmar, what exactly does "Sono scritti sia sul davanti che sul dietro" - forget about the anteriormente, posteriormente bit - actually mean?? The English translation of this as "They are written both in front and in back" is total rubbish to me as a native English person. Your deeper insight would be much appreciated!
OK, those are two different things. 1st one - "Sono scritti sia sul davanti che sul dietro" means "They are (whatever they may be) written on the front and on the back (of something)". Yeah, that's rubbish and I can't really think of an example that makes sense.
2nd one - I just suggested to not spend too much time on analyzing or remembering the usage of "anteriormente" and "posteriormente", because they're fairly rare. When the meaning relates to time, you can simply use "prima" e "dopo" and when they related to a position, "davanti" e "dietro" work just fine.