A recent review of this problem may be found in:
BARKER, J R , BROUARD, S, GASPARIAN, V, IANNACCONE, G, JAUHO, J P, LEAVENS, C R, MUGA, J G, SALA, R, AND SOKOLOVSKY D.
Report on the first European Workshop on Tunnelling Times
Phantoms Newsletter 7 5-10 (1994)
