The chapter "Effects of Couple-stresses in Linear Elasticity" by R. D. Mindlin and H. F. Tiersten explores the impact of couple-stresses on the deformation of continua, a theory initially proposed by Voigt and expanded by E. & F. Cosserat. The authors review the derivations of the Cosserat equations and the associated constitutive equations for finite deformation, highlighting discrepancies between different treatments. They derive the linearized equations and present a uniqueness theorem for the solution of these equations, based on the assumption of positive definiteness of the internal energy-density. The chapter also discusses the additional modulus of elasticity (the ratio of couple-stress to curvature) and its implications for wave propagation, including the existence of non-dispersive dilatational waves and two rotational waves, one of which is non-propagating. The displacement equations of motion are reduced to those of Lamé, and the problem of antisymmetric thickness-shear vibrations of an infinite plate is solved, showing that the natural frequencies exceed the integral.The chapter "Effects of Couple-stresses in Linear Elasticity" by R. D. Mindlin and H. F. Tiersten explores the impact of couple-stresses on the deformation of continua, a theory initially proposed by Voigt and expanded by E. & F. Cosserat. The authors review the derivations of the Cosserat equations and the associated constitutive equations for finite deformation, highlighting discrepancies between different treatments. They derive the linearized equations and present a uniqueness theorem for the solution of these equations, based on the assumption of positive definiteness of the internal energy-density. The chapter also discusses the additional modulus of elasticity (the ratio of couple-stress to curvature) and its implications for wave propagation, including the existence of non-dispersive dilatational waves and two rotational waves, one of which is non-propagating. The displacement equations of motion are reduced to those of Lamé, and the problem of antisymmetric thickness-shear vibrations of an infinite plate is solved, showing that the natural frequencies exceed the integral.