A survey of all letters required for writing correctly all European languages, both official and regional, could already be found in ISO 6937/2:1983. Recently, this information has been checked thoroughly, and a new survey composed based on the present situation. For a clear understanding a distinction was made between letters required for writing words of the language proper, for those derived from other languages, for geographic indications and personal names, for quotations, and for special typographic effects. The result is shown in the Annexes. The tables are taken from a Technical Report by the same author, in which the decisions taken for the classification are fully described and justified. This report "Letters for Europe" can be ordered directly from the Nederlands Normalisatie-Instituut (NNI) in Delft.

Five categories are distinguished, indicated by A to E.
 

A	Letters used for writing words of the language proper,
B	Letters used for writing words of recognizable foreign origin, but adopted into the language,
C	Letters used for writing personal names and geographical indications,
D	Letters used in quotations from foreign languages occurring frequently,
E	Letters resulting from marking a stressed syllable.

 

The shapes of the letters such as are indicated for each language are the official reference shapes. That does not mean that in practice variants are not tolerated. In German one may find for the umlaut sometimes a DOUBLE ACUTE instead of the DIAERESIS, or a BREVE (in handwritten forms) or a small letter e above the vowel letter. Often is for the shape of a diacritic only the difference between "something above" or "something below" of any significance. In that case the BREVE on the Turkish g may look as a CARON or even like a MACRON. A cedilla appears as a comma (or a LOW LINE in Turkish) below the letter or even above it (g in Latvian). One should not become confused by this phenomenon, nor inclined to make more distinctions than in fact exist. The same effects occur in spoken language, with dialectical variants of correct pronunciation. For the right understanding of the story these deviations must be ignored.