. . . . " line with index d is situated between two limits of disjoint runs in the preceding line, i.e. between b and c (see FIG. 7B), then the current, box terminates with (a,b), andan end of box procedure finish-a-box is executed.Otherwise (the ELSE of BB16), the situation is such that the run (a,b) of the preceding line and the run (d,e) of the current line overlap and may together constitute a box, pro" .