V. Mihalache et A. Salomaa, LANGUAGE-THEORETIC ASPECTS OF STRING REPLICATION, International journal of computer mathematics, 66(3-4), 1998, pp. 163-177
The so-called replication operation is studied in the case when severa
l insertion contexts consisting of letters are used, as well as in the
case when this operation is applied to several strings. Some striking
differences, depending on the technical derails of the setup, are obs
erved in the generative power of this operation.