"Equal radii of curvature result in equations for a . Equations of a cylindrical shell are derived when one radius of curvature is set to infinity; when both are set to infinity, it will result in bending of a flat plate. Finally, the ordinary differential equation for bending of a beam is derived when plate width is set to unity."
January 1, 1970
https://en.wikiquote.org/wiki/Thin-shell_structure