Figure 2: Illustration of the centre-of-gravity rule with grey shadings demonstrating material, which must end up in the final sample, lest IEE occur. Upper figure: correct theoretical extraction. Center: correct practical extraction. Bottom picture: incorrect extraction, disobeying the centre-of-gravity rule. Source: Gy, 1993, Pitard, 1993; Smith, 2001; Petersen et al., 2004.