@ARTICLE{
author={Shapovalova Alla I,Popovic Luka C,Burenkov Alexander N,Chavushyan Vahram H,Ilic Dragana J,Kovacevic Andjelka B,Kollatschny Wolfram,Kovacevic Jelena M,Bochkarev Nikolay G,Valdes JR,Torrealba J,Leon-Tavares J,Mercado Abelardo,Benitez E,Carrasco L,Dultzin D,de la Fuente E},
year={2012},
title={Spectral Optical Monitoring of the Narrow-Line Seyfert 1 Galaxy Ark 564},
journal={ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES},
volume={202},
number={1},
pages={-},
document_type={Article},
} 

@ARTICLE{
author={Shapovalova Alla I,Popovic Luka C,Collin S,Burenkov Alexander N,Chavushyan Vahram H,Bochkarev Nikolay G,Benitez E,Dultzin D,Kovacevic Andjelka B,Borisov N,Carrasco L,Leon-Tavares J,Mercado Abelardo,Valdes JR,Vlasuyk VV,Zhdanova VE},
year={2008},
title={Long-term variability of the optical spectra of NGC 4151 - I. Light curves and flux correlations},
journal={ASTRONOMY & ASTROPHYSICS},
volume={486},
number={1},
pages={99-U81},
document_type={Article},
}