1. Saclay-Orsay-Bari-Bologna Collaboration:Nuovo Cimento,29, 515 (1963) (π− incident momentum: 1.59 GeV/c);
2. D. D. Carmony, F. Grard, R. T. Van de Walle andNguyen Huu Xuong:International Conference on High-Energy Physics at CERN (1962), p. 44 (π− incident momentum: 2.03 GeV/c);
3. P. H. Scatterblom, W. D. Walker andA. R. Erwin: preprint (1964) (π− incident momentum: 2.14 GeV/c);
4. V. Hagopian:Thesis (University of Pennsylvania, 1963) (π− incident momentum: 3 GeV/c);
5. J. Kirz, Suh Urk Chung, O. I. Dahl, R. I. Hess, G. R. Kalbfleisch, D. H. Miller andG. A. Smith: preprint (1964) (π− incident momentum: 3.24 GeV/c);