Response to comments by DiGiovanni and Kevan on “Session V: Estimating Likelihood and Exposure”, by Zaida Lentini, Environ. Biosafety Res. 5 (2006) 193–195David I. GustafsonEnviron. Biosafety Res., 7 2 (2008) 111-113DOI: https://doi.org/10.1051/ebr:2008008