This research was partially supported by the Finnish Academy. This project has been supported by the European Commission through the Activity "Access to Large-Scale Facilities " within the Programme "Training and Mobility of Researchers ", awarded to the Instituto de Astrofísica de Canarias to fund European Astronomers' access to its Roque de Los Muchachos and Teide Observatories (European Northern Observatory), in the Canary Islands. E. Benítez, J.A. de Diego & D. Dultzin-Hacyan thank DGAPA-UNAM for support through grant IN-109896. We acknowledge the use of IRAF, distributed by NOAO, which is operated by AURA under cooperative agreement whith the NSF. The Wihuri Foundation has partly financed the monitoring of extragalactic radio sources with the Metsähovi Radio Telescope.
© European Southern Observatory (ESO) 1999
Online publication: April 28, 1999