H. S. M. Coxeter uses a notation that he calls the curtail. This is used to constructed the rectified figures, and those that have these as verticies. I have not mastered yet putting numbers on top of each other but this gives some sort of idea of how the curtail works.
The basis of this notation is as follows.
{ 3, 3 } { 3, 3 }
{3,3,3} { 3, } { 3, }
{ 3, }
0_21 1_21
The figure at the left represents the {3,3,3}. The second figure is the rectified pentatope r{3,3,3}. Here, the thing has been bent back into a "curtail".
Writing p over q for figures like the cuboctahedron and icosadodecahedron are still fairly common, but it is hoped that writing r{p,q} should displace this.
o-----o
/ { 3 3 }
o-----o { 3 }
\ { 3 }
o
1_21
The thing is a topographical nightmare, and even Coxeter abandons it for the shorter forms like 121. My solution to this same issue is a little more radical.
Copyright 2002 Wendy Krieger