M. Danysz, K. Garbowska, J. Pniewski, T. Pniewski, and J. Zakrzewski

• Institute of Experimental Physics, University of Warsaw, Warsaw, Poland
• Institute for Nuclear Research, Warsaw, Poland

E. R. Fletcher

• H. H. Wills Physics Laboratory, University of Bristol, Bristol, England

J. Lemonne, P. Renard^*, and J. Sacton

• Université Libre de Bruxelles, Bruxelles, Belgium

W. T. Toner^†

• CERN, Geneva, Switzerland

D. O'Sullivan, T. P. Shah, and A. Thompson

• Institute for Advanced Studies, Dublin, Ireland

P. Allen, Sr.^‡, M. Heeran, and A. Montwill

• University College, Dublin, Ireland

J. E. Allen, M. J. Beniston^§, D. H. Davis, and D. A. Garbutt

• University College, London, England

V. A. Bull, R. C. Kumar, and P. V. March

• Westfield College, London, England

• ^*Chercheur Agréé à l'Institut Interuniversitaire des Sciences Nucléaires, Belgique.
• ^†Supported by the British Emulsion Committee.
• ^‡Now at University College, London, England.
• ^§Now at the Enrico Fermi Institute for Nuclear Studies, The University of Chicago, Chicago, Illinois.