Latvian orthography  Latvian orthography historically used a system based upon German phonetic principles, while the Latgalian dialect was written using Polish orthographic principles. The present-day Latvian orthography was developed by the Knowledge Commission of the Riga Latvian Association in 1908, and was approved the same year by the orthography commission under the leadership of Kārlis Mīlenbahs and Jānis Endzelīns. Its basis is the Latin script and it was introduced by law from 1920 to 1922 in the Republic of Latvia. For the most part it is phonetic in that it follows the language's pronunciation. Today, the Latvian standard alphabet consists of 33 letters. The modern standard Latvian alphabet uses 22 unmodified letters of the Latin alphabet. The Latvian alphabet lacks "Q", "W", "X" and "Y". These letters are not used in Latvian for writing foreign personal and geographical names; instead they are adapted to Latvian phonology, orthography, and morphology, e. g. "Džordžs Volkers Bušs" (George Walker Bush). However, these four letters can be used in mathematics and sometimes in brand names: their names are "kū", "dubult vē", "iks" and "igrek". The Latvian alphabet has a further eleven letters formed by adding diacritic marks to some letters. The vowel letters "A", "E", "I" and "U" can take a macron to show length, unmodified letters being short. The letters "C", "S" and "Z", which in unmodified form are pronounced , and respectively, can be marked with a caron. These marked letters, "Č", "Š" and "Ž" are pronounced , and respectively. The letters "Ģ", "Ķ", "Ļ" and "Ņ" are written with a cedilla or a small comma placed below (or, in the case of the lowercase "g", above). They are modified (palatalized) versions of "G", "K", "L" and "N" and represent the sounds , , and . Non-standard varieties of Latvian add extra letters to this standard set. The letters F and H appear only in loanwords. Historically the letters CH, Ō and Ŗ were also used in the Latvian alphabet. The last of these stood for the palatalized dental trill which is still used in some dialects (mainly outside Latvia) but not in the standard language, and hence the letter Ŗ was removed from the alphabet on 5 June 1946, when the Latvian SSR legislature passed a regulation that officially replaced it with R in print.