function Eij = getEi(T,i)
Eij = [];
j = i+1;
[nodesi,nodesj]=find(T);
for e=1:length(nodesi)
  e1 = nodesi(e);
  e2 = nodesj(e);
  if ((e1<=i) & (e2>=j))
    Eij = [Eij;[e1 e2]];
  end
end
return