Before revision:  The optimal exercise region of each right (except the last) of the swing option that we consider is characterised in terms of two boundaries which are continuous functions of time and uniquely solve a system of coupled integral equations of Volterra-type.
After revision:  The optimal exercise region of each right (except the last) is described in terms of two boundaries which are continuous functions of time and uniquely solve a system of coupled integral equations of Volterra-type.