Null Lagrangians in linear theories of micropolar type and few other generalizations of elasticity

In the context of linear theories generalized elasticity including those for homogeneous micropolar media, quasicrystals, piezoelectric and piezomagnetic we explore concept null Lagrangians. For obtaining family Lagrangians employ sufficient conditions H. Rund. some cases a non-zero Lagrangian is found stored energy admits split into remainder. However, vanishes whenever relevant tensor obeys certain symmetry which can be construed as an analogue Cauchy relations.