There are no known exceptions in standard Japanese pronunciation, although there are many dialects (such as the Tosa dialect) that preserve the distinction between historical and in speech, usually by using and for historical and and for historical (see Yotsugana). In writing, the distinction is preserved in single morphemes in cases where a sequence ("chidi") or ("tsudu") was historically produced by rendaku (such as in "chidim-u", "shorten", and "tsuduk-u", "continue", pronounced as if "chizim-u" and "tsuzuk-u", respectively), or in compounds where a phonemic or has been voiced to or (such as in "mi-dika" "one's surroundings" and "kana-dukai" "kana usage", pronounced as if "mi-zika" and "kana-zukai", respectively). This usage is a holdover from this rule.