Determination of effective electron yield from swarm and time delay measurements V. Lj. Marković, S. R. Gocić, S. N. Stamenković, Z. Lj. Petrović and M. Radmilović Eur. Phys. J. AP, 14 3 (2001) 171-176 Published online: 15 June 2001 DOI: 10.1051/epjap:2001152