The title problem is studied for the cases: (1) crack-perpendicular tension and crack-parallel shear, (2) plane biaxial load, (3) crack-parallel shear and antiplane shear, and (4) unidirectional load and antiplane shear. All the results are based on a fundamental investigation reported in references [1, 2], the results of which are partly exact, and partly asymptotic and numerical. Neither the maximum-stress nor the minimum-strain-energy-density criterion indicates a coupling between plane and antiplane loads.