“…Degenerate scales of the plane elasticity were studied by Chen et al (2009a, 2009b, 2009c). Corfdir and Bonnet (2016) used the complex variable methods to find the exact degenerate scales in plane elasticity. To deal with degenerate scales, there are several regularized approaches, e.g., the method of adding rigid body mode (Chen et al , 2005a, 2014), rank promotion by adding the boundary flux equilibrium (Chen et al , 2014), hypersingular integral formulation (Chen et al , 2014), CHEFF method (Chen et al , 2002, 2005a; Chen et al , 2014), the Fichera’s method (Chen et al , 2014) and the self-regularization method (Chen et al , 2017a).…”