The geographic names in countries in which the Roman character is employed in writing (which includes the néo-Latin, Germanic, and Scandinavian languages) shall be written in the orthography of the country to which they belong.
The following rules apply solely to geographic names in countries without a written language, and to geographic names in countries where another than the Roman character is employed in writing.
Names of places for which the orthography, through long usage, has become consecrated shall, however, be excepted from the rules. Examples: La Mecque, Naples, Calcutta.
The rules in detail are:
1. The vowels a, e, i, and o are pronounced as in French, Spanish, Italian, and German. The letter e shall never be mute.
2. The French sound of u shall be represented by u with a tréma like the German ü.
3. The French sound ou shall be represented by u, as in Italian, Spanish, and German.
4. The French sound eu shall be represented by the character oe [ligated] and be pronounced as in oeil.
5. The lengthening of a vowel sound shall be indicated by the 'accent circonflexe' (^), and the shortening by an 'apostrophe' (').
6. The consonants b, d, f, j, k, l, m, n, p, q, r, t, v, and z are pronounced as in French.