**4. Theory of Scale Functions**

Again the reader is invited to compare the exposition of the following section with that of (Bertoin 1996, sct. VII.2) and (Kyprianou 2006, sct. 8.2), which deal with the spectrally negative case.

<sup>2</sup> It is part of the condition, that such an *x* should exist (automatically, given the preceding assumptions, there is at most one).
