Consider the following expressions, which are identical except that in ex2, the last Gamma matrix has "t" instead of "e". But, the combine for the second expression is giving some strange output.

```
ex:=(\Gamma_r)_{\alpha\beta} (\Gamma_{r t u} \Gamma_{e v h})_{\beta\gamma};
ex1:=(\Gamma_r)_{\alpha\beta} (\Gamma_{r t u} \Gamma_{t v h})_{\beta\gamma};
combine(ex);
combine(ex1);
```

I think part of the problem in the second case is illustrated by

`ex3:= (\Gamma_{r t u} \Gamma_{t v h})_{\beta\gamma};`

which tries to combine the t and t contraction?