Bonito , Andrea and Lei , Wenyu. (2022). Approximation of the Spectral Fractional Powers of the Laplace-Beltrami Operator.
            <i>Numerical Mathematics: Theory, Methods and Applications</i>. <i>15</i> (4).
            1193-1218.
         doi:10.4208/nmtma.OA-2022-0005s