ESDU 80023 defines the specially-orthotropic plate. Buckling loads are presented in terms of the plate geometry and the four flexural stiffnesses for a variety of edge conditions for plates loaded in uniaxial or biaxial compression@ shear and shear with uniaxial compression. The analysis assumes the through-thickness shear stiffness is sufficiently large for the bending stiffnesses to control buckling. A criterion is given to check whether that is so and@ if it is not met@ the program of ESDU 81047 or ESDU 94005 (ESDUpac A8147 or ESDUpac A9405) should be used; those programs include the effect of shear stiffness.