@article { 4914,
	title = {Detection of the cosmic ?-ray horizon from multiwavelength observations of blazars},
	year = {2013},
	publisher = {ApJ},
	author = {A. Domínguez and J. D. Finke and F. Prada and J. R. Primack and F. S. Kitaura and B. Siana and D. Paneque}
}