Kana Extended-A is a Unicode block containing hentaigana (non-standard hiragana) and historic kana characters. Additional hentaigana characters are encoded in the Kana Supplement block.
Anderson, Deborah; Whistler, Ken; McGowan, Rick; Pournader, Roozbeh; Glass, Andrew; Iancu, Laurențiu; Moore, Lisa (2016-07-30), "6.a", Recommendations to UTC #148 August 2016 on Script Proposals
Anderson, Deborah; Whistler, Ken; Pournader, Roozbeh; Moore, Lisa; Liang, Hai (2020-01-10), "11a.", Recommendations to UTC #162 January 2020 on Script Proposals
Anderson, Deborah; Whistler, Ken; Pournader, Roozbeh; Moore, Lisa; Constable, Peter; Liang, Hai (2020-07-21), "22. Kana", Recommendations to UTC #164 July 2020 on Script Proposals