When you go to the Archives bring your identity card (passport). It is also desirable to have a letter from the institution that is sending you or a letter of recommendation from your university school (institute). If you want to view geological maps, you should bring a letter from the institution you are working for, explaining the purpose of your study of the maps. Holdings created less than 30 years ago may be used only for the needs of their creators or state.
Now you are here – learn the usual procedure.