Evaluating the performance of a refrigerator by an external system using entanglement Y. Khlifi, A. El Allati, A. Salah and Y. Hassouni Eur. Phys. J. D, 75 7 (2021) 195 Published online: 01 July 2021 DOI: 10.1140/epjd/s10053-021-00211-7