Measurement of the charged pion mass using X-ray spectroscopy of exotic atoms oleh M. Trassinelli, D.F. Anagnostopoulos, G. Borchert, A. Dax, J.-P. Egger, D. Gotta, M. Hennebach, P. Indelicato, Y.-W. Liu, B. Manil, N. Nelms, L.M. Simons, A. Wells