We prove, for transport equations with sources, a series of results of
the following type: There exists a classe C of bounded measures on th
e velocity space V such that for each d mu epsilon C there exists a me
asure d mu' on V such that the knowledge of the moments of the solutio
n with respect to d mu and d mu' determines explicitly the source. As
by products we obtain W-2,W-p regularity results for moments with resp
ect to measures d mu epsilon C.