Author,Title,Journal,ISSN,Publisher,Date,Volume,Number,Page,URL,URL(DOI) Seiji Kojima,Relativistic Two-Particle System and Spin-Mass Relations of Meson,Progress of theoretical physics = 理論物理学の進歩,0033068X,Kyoto : Publication Office,1979-03,61,3,p960-970,https://cir.nii.ac.jp/crid/1524232505729011584,https://doi.org/10.1143/ptp.61.960