Abaqus UMAT, DDSDDE calculation for hyperelastic material

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Hi, I am trying to implement hyperelastic constitutive model in
Abaqus using UMAT subroutine. I have gone through the theory manual (section
4.6.1) of Abaqus 6.12. I am finding it difficult to understand few steps (see attchment),
mainly related to the calculation of DDSDDE. How do we calculate variations of
different strain measures? I am looking forward to your suggestions regarding
any study material that will help me understand this.

Thanks 

Priyank

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