1. International Conference on High Energy Accelerators and Instrumentation — CERN 1959, Proceedings;Ticho,1959
2. C. Weigand (private communication).
3. Proceedings of an International Conference on Instrumentation for High Energy Physics Berkeley;Sard,1960-1961
4. In a modification of Sard's apparatus, Kerth has replaced the polaroid film by an image orthicon (Z 5294) viewing a sheet of sodium iodide through an f/1.1 lens and reports a sensitivity possibly as high as 104 particles per cm2 per second.