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2. L. Calabi and W.E. Hartnett, “Some general results of coding theory with applications to the study of codes for the correction of synchronization errors,” Information and Control 15,3 (Sept 1969) 235–249. Reprinted in: W.E. Hartnett (ed), Foundations of Coding Theory (1974) Chapter 7, pp.107-121.
3. V.I. Levenshtein, “Binary codes capable of correcting deletions, insertions and reversals,” Soviet Phys. Dokl. 10 (1966) 707–710.
4. V.I. Levenshtein, “Elements of the coding theory,” in: Discrete Math. and Math. Probl. of Cybern., Nauka, Moscow (1974) 207–235 (in Russian).
5. V.I. Levenshtein, “On perfect codes in deletion and insertion metric,” Discrete Math. Appl. 2,3 (1992) 241–258. Originally published in Diskretnaya Matematika 3,1 (1991) 3-20 (in Russian).