Hartill, Donald L. (1967) Experimental study of antiproton-proton annihilation into electron-positron pair and antiproton-proton annihilation into two [gamma]-rays for incident antiproton momenta of 1.50 GeV/c and 2.50 GeV/c (Dissertation (Ph.D)), California Institute of Technology doi: 10.7907/76YC-XC89