*2.1.5 General linear inverse problems*

All the examples of the linear inverse problems listed above, can be summarized in the following general form:

$$\mathbf{g}(\mathbf{s}) = \int f(\mathbf{r}) \, h(\mathbf{s}, \mathbf{r}) \, \mathrm{d}\mathbf{r} \tag{7}$$

where *s* can be either *t*,ð Þ *x*, *y* ,ð Þ *r*, *ϕ* or (*u*, *v*) and *r*, respectively *τ*, *x*<sup>0</sup> , *y*<sup>0</sup> ð Þ,ð Þ *x*, *y* and (*x*, *y*).
