the placement of stress and length of vowels: Long stressed vowels are notated with an acute diacritic: á é í ó ú ŕ (IPA: ). However, the rarer long stressed low-mid vowels and are notated with a circumflex: ê ô. Short stressed vowels are notated with a grave: à è ì ò ù (IPA: ). Some systems may also include ə̀ for . Tonemic diacritics The tonemic system uses the diacritics somewhat differently from the non-tonemic system. The high-mid vowels and are written ẹ ọ with a subscript dot, while the low-mid vowels and are written as plain e o. Pitch accent and length is indicated by four diacritical marks: The acute ( ´ ) indicates long and low pitch: á é ẹ́ í ó ọ́ ú ŕ (IPA: ). The inverted breve ( ̑ ) indicates long and high pitch: ȃ ȇ ẹ̑ ȋ ȏ ọ̑ ȗ ȓ (IPA: ). The grave ( ` ) indicates short and low pitch. This occurs only on è (IPA: ), optionally written as ə̀. The double grave ( ̏ ) indicates short and high pitch: ȁ ȅ ȉ ȍ ȕ (IPA: ). ȅ is also used for , optionally written as ə̏. The schwa vowel is written ambiguously as e, but its accentuation will sometimes distinguish it: a long vowel mark can never appear on a schwa, while a grave accent can appear only on a schwa. Thus, only ȅ and unstressed e are truly ambiguous. Regulation Standard Slovene spelling and grammar are defined by the Orthographic Committee and the Fran Ramovš Institute of the Slovene Language, which are both part of the Slovenian Academy of Sciences and Arts (Slovenska akademija znanosti in umetnosti, SAZU). The newest reference book of standard Slovene spelling (and to some extent also grammar) is the Slovenski pravopis (SP2001; Slovene Normative Guide). The latest printed edition was published in 2001 (reprinted in 2003 with some corrections) and contains more than 130,000 dictionary entries. In 2003, an electronic version was published. The official dictionary of modern Slovene, which was also prepared by SAZU, is Slovar slovenskega knjižnega jezika (SSKJ; Standard Slovene Dictionary). It was published in five volumes by Državna Založba Slovenije between 1970 and 1991 and contains more than 100,000 entries and subentries with accentuation, part-of-speech labels, common collocations, and various qualifiers. In the 1990s, an electronic version of the dictionary was published and is available online.