Trace norm quantum discord for two qubits: the complete solution revisited and applications Piotr Ługiewicz and Alicja Gronowska-Kowalska Eur. Phys. J. Plus, 137 5 (2022) 599 Published online: 17 May 2022 DOI: 10.1140/epjp/s13360-022-02822-4