Lihui Chai, Shi Jin and Peter A. Markowich. (2018). A Hybrid Method for Computing the Schrödinger Equations with Periodic Potential with Band-Crossings in the Momentum Space.
            <i>Communications in Computational Physics</i>. <i>24</i> (4).
            989-1020.
         doi:10.4208/cicp.2018.hh80.01