R. Nageshwar Rao & P. Pramod Chakravarthy. (2020). A Fitted Numerov Method for Singularly Perturbed Parabolic Partial Differential Equation with a Small Negative Shift Arising in Control Theory.
            <i>Numerical Mathematics: Theory, Methods and Applications</i>. <i>7</i> (1).
            23-40.
         doi:10.4208/nmtma.2014.1316nm