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