Jiong Zhong, Remco Duits, Gonzalo Sanguinetti and Bart M. ter Haar Romeny. (2016). Numerical Approaches for Linear Left-Invariant Diffusions on $SE(2)$, Their Comparison to Exact Solutions, and Their Applications in Retinal Imaging.
            <i>Numerical Mathematics: Theory, Methods and Applications</i>. <i>9</i> (1).
            1-50.
         doi:10.4208/nmtma.2015.m1411