Valentini's papers are entitled "Signal-locality, uncertainty and
the Subquantum H-theorem" parts 1 and 2, and were published in
Physics Letters A:

part 1: Vol.156 No.1-2 pp.5-11
part 2: Vol.158 No.1-2 pp.1-8

His Ph.D. thesis from SISSA, Trieste, goes into the subtleties in
considerably more detail.