... The hard gamma radiation from AGN is produced most probably in the relativistic jets observed in the considerable part of these objects. In the center of AGN (and may be of all other galaxies) there is a supermassive black hole surrounded by the accretion disk, which is the source of the energy in these objects. ... The problem of particle acceleration in the AGN jets is very important: the time of the electron energy losses in the jets is usually much less than their life time. ... next page . ...