Fig. 1From: Standardisation, calibration and correlation of the Kübler-index and the vitrinite/bituminite reflectance: an inter-laboratory and field related studyCorrelation between standards used by B. Kübler and re-measured in Frankfurt by R. Petschick (Petschick 1989). The same standards were used in Basel for the present study and the correlation was nearly 1:1, n = 10, r = 0.982 (not shown)Back to article page