(en) David J. Birnbaum, « Standardizing characters, glyphs, and SGML entities for encoding early Cyrillic writing », Computer Standards & Interfaces, vol. 18, no 3, , p. 201–252 (DOI10.1016/0920-5489(95)00096-8)
(en) Michael Everson, David Birnbaum, Ralph Cleminson, Ivan Derzhanski, Vladislav Dorosh, Alexej Kryukov, Sorin Paliga et Klaas Ruppel, Proposal to encode additional Cyrillic characters in the BMP of the UCS (no N3194R, L2/07-003R), (lire en ligne)
(ru) В. С. Голышенко, Мягкость согласных в языке восточных славян XI-XII вв., Москва, Наука,