V.N. Biktashev, “Drift of a reverberator in an active medium due
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Evolution, eds. A.V. Gaponov-Grekhov, M.I. Rabinovich, pp. 316–324,
Nauka, Moscow, 1989 (in Russian),
in Nonlinear Waves II. Dynamics and evolution, pp. 87–96,
eds A.V. Gaponov-Grekhov, M.I. Rabinovich
and J. Engelbrecht, Springer, Berlin, ISSN 978-3-642-74366-5,
1989 (English version).