Combining diaerasis below can be used for presenting some romanizations of Min Chinese dialects. Coping the following string into LibreOffice, then they does not work except U, also not work with additional diacritics. Converting them into lowercase would get the same effects.
A̤Ă̤Ā̤A̤̍Á̤À̤Â̤Ǎ̤E̤Ĕ̤Ē̤E̤̍É̤È̤Ê̤Ě̤O̤Ŏ̤Ō̤O̤̍Ó̤Ò̤Ô̤Ǒ̤ṲṲ̆Ṳ̄Ṳ̍Ṳ́Ṳ̀Ṳ̂Ṳ̌