**8. Circularity or Not Circularity?**

Even though GRBs could be thought of as indicators toward the determination of the universe's expansion history, it is remarkable to stress that small redshift GRB data are still missing. Consequently, if one requires to calibrate GRBs with small redshift data, there is the strict need of other data sets, whose data points lie around *z* ' 0 that permit performing the calibration procedure. The calibration procedure is essentially a consequence of the correlation functional forms that, by virtue of the above considerations, are commonly written as *y* = *a x* + *b*, with *a*, *b* real constants that depend upon the relation itself. Bearing this in mind, we focus below on different calibration strategies. In this respect, we highlight whether it is absolutely necessary or not to calibrate our correlations in order to confront cosmological models with GRB data. Below, we start with such considerations, critically discussed.
