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\bibitem{Beltrame_etal2011} Beltrame, P. et al, Oliver, J. F., Rafecas, M., \& Solevi, P. (2011). The AX-PET demonstrator-Design, construction and characterization. \textit{Nucl. Instrum. Methods Phys. Res. A}, \textit{654}(1), 546--559.

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