  We analyze the data of the observations of the radio sources frequently found
in space. They are believed to be the sets of molecular condensations each of
which works as a maser, so that the whole set produces a characteristic
spectrum. It turns out that in some cases the intensity of one of the
components of such spectrum corresponding to a single condensation changes
periodically with a period of dozens of minutes or of hours.

Instrumentation and Methods for Astrophysics