finite element method – How to access implementations of MaterialModel?

In the documentation for Hyperelasticity there is an example of the MaterialModel for NeoHookean and the St Venant Kirchoff models. These are very useful in helping develop ones own materials models. I would like to modify the NeoHookean model to include thermal strains which would allow more accurate simulations of large deformations. To do this it would also be useful to see how the MaterialModel for the small strain elasticity models where thermal strains are included.

How can one access these MaterialsModels (i.e. Orthotropic Elasticity etc…) ?