theorem
 width G > 1 & i in Seg width G implies DelCol(G,i) is not empty-yielding
proof assume that
A1: width G > 1 and
A2:i in Seg width G;
  width DelCol(G,i)+1 > 0+1 by A1,A2,Th64;
  then
A3: width DelCol(G,i) > 0;
  then len DelCol(G,i) > 0 by Def3;
 hence DelCol(G,i) is not empty-yielding by A3;
end;
