Residual error estimation for anisotropic Kirchhoff plates

Residual error estimation for conforming finite element discretisations of the isotropic Kirchhoff plate problem is covered by an estimator of Verfürth for the related biharmonic equation. This article generalises Verfürth's result to Kirchhoff plates with an anisotropic material, which requires some modifications. Special emphasis is laid on the reduced Hsieh-Clough-Tocher triangular finite element, the conforming element with the least possible number of unknowns.