How to compute the degrees of freedom in SFA

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I want to test for differences between the group frontiers,the null hypothesis is that the group frontiers are identical.

Suppose the generalised likelihood-ratio test statistic for the null hypothesis that the group frontiers are identical is LR = 140.6.

Assume that parameters=22 and group=4, how to compute the "degrees of freedom" of chi-square distribution to test the null hypothesis?