  The paper investigates the general case of incompressible non-classical
elasticity with small deformations and rotations. It is shown that the internal
spin rotations are important only when a specific Born term is presented in the
free energy. The thermodynamic stability conditions and existence of soft
deformational modes are analysed for free energy with three rotational degrees
of freedom and scalar order parameter. It is shown that the soft deformation
modes do not always exist. If the conditions for existence of soft modes are
satisfied and the Born term is absent, the stress tensor is proved to be
symmetric. It is shown that the infinitesimal Warner potential satisfies these
conditions. When the stress symmetry could be assumed only approximately, a
simplified, "reduced" relations are derived for the free energy and stress. The
reduce formulation, which preserves the general stability conditions and the
condition for existence of soft deformations, also allows easy calculations of
stress-strain-rotation relations.
