Mitankin, P., S. Mihov, and Kl. Schulz. 2009. “Universal Levenshtein Automata for a Generalization of the Levenshtein Distance”. Ann. Sofia Univ. Fac. Math. And Inf. 99 (December):5-23. https://ftl5.uni-sofia.bg./index.php/fmi/article/view/109.