Right, along this line, the first one I hit was the kronecker delta - I couldn't see the comma between the \delta_{i,j}. It was only after going through until I

Right, along this line, the first one I hit was the kronecker delta - I couldn't see the comma between the \delta_{i,j}. It was only after going through until I found it again and zooming in I could see the problem. Fun thing though.