K S and K L interference in the π +π - decay mode, CP invariance and the K S-K L mass difference Alff-Steinberger, C. ; Heuer, W. ; Kleinknecht, K. ; Rubbia, C. ; Scribano, A. ; Steinberger, J. ; Tannenbaum, M. J. ; Tittel, K. Abstract Publication: Physics Letters Pub Date: February 1966 DOI: 10.1016/0031-9163(66)90937-1 Bibcode: 1966PhL....20..207A