Aharonian, F., Akhperjanian, A., Anton, G., Barres de Almeida, U., Bazer-Bachi, A., Becherini, Y., …et al. (2009). Simultaneous Observations of PKS 2155-304 with HESS, Fermi, RXTE, and Atom: Spectral Energy Distributions and Variability in a Low State. Astrophysical Journal, 696, L150-L155. https://doi.org/10.1088/0004-637x/696/2/l150