Time variations of the ON2 water maser spectrum during 1981-1995 E. E. Lekht, A. Marquez and J. E. Mendoza-Torres Astron. Astrophys. Suppl. Ser., 120 3 (1996) 415-422 Published online: 15 December 1996 DOI: 10.1051/aas:1996303