Negative Pion Production from Neutrons by Polarized gamma Rays - Nishikawa, T.; Hiramatsu, S.; Kimura, Y.; Kobayashi, M.; Kondo, K.; Okumura, S.; Suzuki, T.; Takikawa, K.; Tsuru, T.; Yoshida, H. (Phys. Rev. Lett., 1968)