Variability of the H2O maser associated with the M-supergiant S Persei E. E. Lekht, G. M. Rudnitskij, J. E. Mendoza-Torres and A. M. Tolmachev A&A, 437 1 (2005) 127-133 Published online: 10 June 2005 DOI: 10.1051/0004-6361:20052635