Hassan Yousefi, Seyed Shahram Ghorashi and Timon Rabczuk. (2018). Directly Simulation of Second Order Hyperbolic Systems in Second Order Form via the Regularization Concept.
            <i>Communications in Computational Physics</i>. <i>20</i> (1).
            86-135.
         doi:10.4208/cicp.101214.011015a