Qiang Zhang, Maoqi Cao, Xiaobin Shan, Yuquan Li, Zhenya Wang & Liusi Sheng. (1970). Study on $H_3^+$ Formation by Synchrotron Radiation.
            <i>Journal of Atomic and Molecular Sciences</i>. <i>5</i> (2).
            148-155.
         doi:10.4208/jams.042813.070213a