DefinitionA <CANONICALLY PARAMETERISED INNER DEGENERATE TOROIDAL SURFACE> is an <INNER DEGENERATE TOROIDAL SURFACE> and a <PARAMETERISED SURFACE> and an <U UNBOUNDED SURFACE> and a <V UNBOUNDED SURFACE> if and only if: it is an <INNER DEGENERATE TOROIDAL SURFACE>; it is a <PARAMETERISED SURFACE>; it is a <U_UNBOUNDED SURFACE>; it is a <V_UNBOUNDED SURFACE>; it is a part of a self intersecting <CANONICALLY PARAMETERISED TOROIDAL SURFACE>