Q:Information:  - Russian orthography is formally considered to encompass spelling and punctuation. Russian spelling, which is quite phonemic in practice, is a mix of the "morphological" and "phonetic" principles, with a few "etymological" or "historic" forms, and occasional "grammatical" differentiation. The punctuation, originally based on Byzantine Greek, was in the seventeenth and eighteenth centuries reformulated on the French and German models.  - The letter  (italics "", "") of the Cyrillic script, also spelled jer or er, is known as the "hard sign" (  ) in the modern Russian and Rusyn alphabets, as "er golyam" ( , "big er") in the Bulgarian alphabet, and as "debelo jer" ( , "fat yer") in pre-reform Serbian orthography. The letter is called back yer or back er in the pre-reform Russian orthography, in Old Russian, and in Old Church Slavonic. Originally the yer denoted an ultra-short or reduced middle rounded vowel. It is one of two reduced vowels that are collectively known as the yers in Slavic philology.  - Old Church Slavonic, also known as Old Church Slavic (often abbreviated to OCS; self-name , "slovnsk jzyk"), was the first Slavic literary language. The 9th-century Byzantine missionaries Saints Cyril and Methodius of Slavic, Greek descent, or both, are credited with standardizing the language and using it in translating the Bible and other Ancient Greek ecclesiastical texts as part of the Christianization of the Slavs. It is thought to have been based primarily on the dialect of the 9th century Byzantine Slavs living in the Province of Thessalonica (now in Greece). It played an important role in the history of the Slavic languages and served as a basis and model for later Church Slavonic traditions, and some Eastern Orthodox and Eastern Catholic churches use this later Church Slavonic as a liturgical language to this day. As the oldest attested Slavic language, OCS provides important evidence for the features of Proto-Slavic, the reconstructed common ancestor of all Slavic languages. History. The language was standardized for the mission of the two apostles to Great Moravia in 863 (see Glagolitic alphabet for details). For that purpose, Cyril and his brother Methodius started to translate religious literature to Old Church Slavonic, allegedly based on the Slavic dialects spoken in the hinterland of their hometown, Thessaloniki, in the today's Greece.  - Neutral Yer ( Majuscule :  , Minuscule :  ) is used in transcribing documents when it is hard to tell the difference between a  and a  . It was common in Late Medieval Russian archival materials and scripts . The appearance looks like a Yer with a hook on the top .  - A yer is one of two letters in Cyrillic alphabets, namely  (, "jer") and  (, "jer"). The Glagolitic alphabet used as their respective counterparts the letters and . They originally represented phonemically the "ultra-short" vowels in Slavic languages (including Old Church Slavonic), collectively known as the yers. In all Slavic languages they either evolved into various "full" vowels or disappeared, in some cases leaving palatalization of adjacent consonants. At present, the only Slavic language that uses "" as a vowel sign (pronounced //) is Bulgarian (although in many cases it corresponds to earlier "", originally pronounced /õ/). Many languages using the Cyrillic alphabet have kept one or more of the yers to serve specific orthographic functions.  - The Bulgarian alphabet is used to write the Bulgarian language.  - The Cyrillic script is a writing system used for various alphabets across eastern Europe and north and central Asia. It is based on the Early Cyrillic, which was developed in the First Bulgarian Empire during the 9th century AD at the Preslav Literary School. It is the basis of alphabets used in various languages, past and present, in parts of southeastern Europe and northern Eurasia, especially those of Slavic origin, and non-Slavic languages influenced by Russian. , around 252 million people in Eurasia use it as the official alphabet for their national languages, with Russia accounting for about half of them. With the accession of Bulgaria to the European Union on 1 January 2007, Cyrillic became the third official script of the European Union, following the Latin script and Greek script.    What entity does 'neutral yer' has the relation 'part of' with?
A:
cyrillic script