“…An important special case of the system defined by Eqs. A number of papers have been published on first-passage problems for integrated processes (see, e.g., Hesse [5], Lachal [8], Lefebvre [9,10]). Then, under appropriate smoothness conditions on the functions / a n d a (see, e.g., Arnold [2, p. 152]), the j>(0 process is a diffusion process.…”