15. The process according to claim 12 where the maximum probable frequency, f.sub.max, and the minimum probable frequency, f.sub.min, are calculated in accordance with the relationships ##EQU6## where n.sub.i is the number of gaps between documents in the sample containing the selected representation, n.sub.c is the number of documents in the collection, x.sub.i is the number of documents in the sample, s.sub.i is the greater of x.sub.i /n.sub.i or the standard deviation of the n.sub.i gaps, and z is the standard critical value for normal distribution for a preselected reliability.
15. The process according to claim 12 where the maximum probable frequency, f.sub.max, and the minimum probable frequency, f.sub.min, are calculated in accordance with the relationships ##EQU6## where n.sub.i is the number of gaps between documents in the sample containing the selected representation, n.sub.c is the number of documents in the collection, x.sub.i is the number of documents in the sample, s.sub.i is the greater of x.sub.i /n.sub.i or the standard deviation of the n.sub.i gaps, and z is the standard critical value for normal distribution for a preselected reliability. 19. The process according to claim 15 where the preselected reliability is 0.995 and z is 2.8070.