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ABSTRACT. Some selected aspects of current research into active galactic nuclei (AGN) are reviewed. Included topics are the continuum, the broad emission line region and the existence of black holes in galactic nuclei. It is found that an increasing number of observations indicates the presence of accretion disks around massive black holes.
Key Words: active galaxies, black holes, accretion disks, variability, broad line region
Table of Contents
INTRODUCTION
THE CONTINUUM
The IR Continuum
The Optical-UV Continuum
The X-ray Continuum
The Soft Excess
The Hard X-ray Power Law
X-ray Reflection and Absorption
The 
-ray Continuum
THE BROAD-LINE REGION
Observational Methods
The Standard BLR Model
Recent Developments
The NGG 5548 and 4151 Campaigns
The Accretion Disk Model
THE CENTRAL BLACK HOLES IN ACTIVE GALACTIC
NUCLEI
Formation
Methods of Inferring the Mass
CONCLUSIONS
REFERENCES
