  We show that if $(X_s, s\geq 0)$ is a right-continuous process,
$Y_t=\int_0^t\d s X_s$ its integral process and $\tau = (\tau_{\ell}, \ell \geq
0)$ a subordinator, then the time-changed process $(Y_{\tau_{\ell}}, \ell\geq
0)$ allows to retrieve the information about $(X_{\tau_{\ell}}, \ell\geq 0)$
when $\tau$ is stable, but not when $\tau$ is a gamma subordinator. This
question has been motivated by a striking identity in law involving the Bessel
clock taken at an independent inverse Gaussian variable.
