What do A pos and C pos mean?
The # column is the rank of each listed entry for Max Planck Society — rank 1 means this entry is where Max Planck Society has the most articles or citations. A pos and C pos show the reciprocal: the position of Max Planck Society within that entry's own ranked list, by articles and citations respectively. A low value means Max Planck Society is among the most prominent contributors for that entry.
