On kaonic hydrogen. Quantum field theoretic and relativistic covariant approachA. N. Ivanov, M. Cargnelli, M. Faber, J. Marton, N. I. Troitskaya and J. ZmeskalEur. Phys. J. A, 21 1 (2004) 11-28DOI: https://doi.org/10.1140/epja/i2003-10178-y